No physical relationship stays mind-blowing in the long term - but neither should it die out altogether. Our reporter examines the most common reasons for an extinguished sex life and asks the experts how couples can relight the fire…
But that's not an excuse to chalk a disappointing sex life up as 'just one of those things'. If you've read all the above and reckon your expectations are reasonable but not being met, then there's no reason to suffer in silence.
Most important to solving the problem is to pinpoint why the sexual side of your life is out of sync. This could be any number of factors says Bergin; stress, depression, negative body image, infidelity, illness, overuse of porn, the arrival or children, menopause, and unresolved conflict.
"When we consider that we can experience any, or several, of these issues during a lifetime, then it's likely that our sexual relationships will hit lulls and rocky patches."
Sexual and relationship therapist Tony Duffy (tonyduffy.com) identifies these three key reasons why a couple's sex life can start to flag.
The relationship buffer zone wears away: "I describe this as like the protective padding around the couple," he explains. "It contains the essential elements for the relationship like honesty, trust and respect with love the glue that holds these elements together."
Familiarity breeds contempt, with sex becoming predictable and boring.
Work gets in the way, with children, bills, illness or even a death in the family all playing a part in putting stress in a relationship and knocking sex onto the sidelines.
The arrival of children on the scene is a common factor, with last year's Maternal Health and Maternal Morbidity in Ireland study revealing that, while 51pc of mums had reported being 'very satisfied' with their sex life pre-pregnancy, only 24pc reported the same 12 months post-partum.
The best way to pinpoint the problem, and the only way to solve it, is to talk - with your partner, a therapist, or both.
"Talk, talk, talk," insists Duffy. "Talk about how you feel, what is going on for you, what you need from your partner, what you want - sexually and non-sexually. Couples who are able to talk to each other about their sexual needs have more satisfaction in this area than those who don't."
"Potential problems are scary to acknowledge, that's the real challenge for a lot of people," adds O'Reilly. "We are afraid and the fear of shame and rejection means we often choose to remain silent on matters sexual."
She feels our coyness about sexuality is a cultural issue, something that will need to be addressed in school sex education and on a wider societal level before we become more comfortable. Bergin agrees. "These conversations can be tricky, couples don't want to hurt each other and there's often embarrassment, after all, we've never really been taught how to talk about sex in an open way."
It might mean feeling vulnerable, or risking rejection, but done sensitively, it is possible to have a successful conversation about sex. To tackle sex talk sensitively and successfully, she has these key recommendations:
Choose a time carefully. When you're relaxed and won't be interrupted.
Listen. You might have lots to say but try to listen to how your partner sees it, where they're at and how they're feeling.
Avoid blaming. Use 'I' statements to own your emotions.
Accept. Be gentle with your partner and realise they may find this hard to talk about.
Explore options. "Together you can discuss if you need to prioritise or put a plan in place that allows you more time for intimacy," says Bergin. "Once you've opened up the lines of communication together, it's easier to revisit the topic."
Researchers have come up with multiple factors reputed to boost sexual satisfaction, with polls suggesting that everything from better sleep to wearing socks in bed can result in women's increased sexual pleasure. But in most cases, the steps towards establishing a better sex life will take time.
And it's worth it - the importance of a healthy, fulfilling sex life should not be underestimated. "Sex is very important to our general well-being," explains Bergin. "Oxytocin, a hormone released during sex, helps us to feel closer, more relaxed and allows us to bond more easily so it has an enhancing effect on a relationship as a whole.
"Endorphins released during sex are a de-stressor and time spent together sexually allows us to have fun and take a break from the pressures of life. It can be seen too as exercise and has cardiovascular benefits. Sex helps us sleep better due to the hormone prolactin being released after orgasm, and it can also help if we're experiencing pain.
"Finally, people who have sex regularly are found to have higher levels of Immunoglobulin A, which is an antibody that helps us avoid cold and flu."
"Our sex lives are inextricably linked to our emotional lives," adds O'Reilly. "Some of us need to be emotionally secure and happy in order to engage fully sexually, some need to engage fully in order to feel secure and happy. For most of us it can be both."
But solving these issues might require the help of a third party. We're happy to ask life coaches, personal trainers and dating apps for help with problems in other aspects of life - sex should be no different.
"In therapy I see enormous relief when people start discussing and talking about sex and sexuality," says Bergin. "Talking about sex helps us normalise and understand problems when they occur, and it helps us understand our own likes, dislikes and boundaries."
O'Reilly agrees. "Even one session with a couples therapist can be enormously beneficial. And maybe even fun."
Top 5 causes of a stale sex life
These are the most common issues facing couples, says sex therapist Teresa Bergin
Lack of communication around sex
5 ways to sex up your relationship
It depends on the individual couple - and the issues they've uncovered through communication - but some general steps to restore intimacy are:
Turn off the TV and ban screens from the bedroom.
Don't get fixated on having 'perfect' sex - of the full-on sexy lingerie weekend away-type. Instead focus on doing something affectionate every day and build intimacy.
Consider a sex schedule - weekly, not daily - to put sex back on the priority list. Research has showed that having sex can improve your libido.
Don't postpone passion. If you feel the urge, act on it rather than waiting until you've done the laundry / made the dinner / hoovered the house. Of course this isn't always practical but it's good to act on the spark rather than hope desire will still be burning later.
See your GP. Last year a study found that one third of men still won't go to their doctor to discuss a loss of sex drive because they're too embarrassed. One in 10 men suffers from erectile dysfunction, vaginismus (causing pain during sex) is common in women - and both can be helped by seeking the advice of a health professional. A drop in libido can also be symptomatic of other, non-sexual, health problems, including arthritis, cancer, diabetes, high blood pressure and neurological diseases. Get help, that's what the professionals are there for.
What NOT to do when dealing with a flagging sex life
Don't get into blame or criticism - both are extremely corrosive.
Don't compare yourself to other people, ex-partners or porn. Genital size, duration of sex, frequency of sex, body shape - there is no normal, only your normal. Taking cues from porn or other sources only results in personal hang-ups and insecurities in the bedroom.
Don't put too much emphasis on the big O. "Too often couples get hung up on this," says Teresa Bergin. "If orgasm happens, great. But when there's too much focus and pressure on orgasm, it actually makes it less likely to occur.
Don't introduce sex toys or pornography without prior discussion.
Don't bottle up feelings about lack of intimacy, it only leads to resentment and further alienation.
The joys of sex (beyond the obvious)
Good for stress-busting
Good for bonding
Boosts the immune system
Lower blood pressure
Strengthens pelvic floor muscles (improving female bladder control)
May reduce risk of prostate cancer