Good question.
There's a lot of these types of relationships that have lasted.
But I've never understood why people see a long relationship as automatically a successful one.
Or a seemingly happy relationship as a one without problems.
Or, and people who've never experienced a breakdown of this type of relationship might read this and think I'm being patronising - please know that's absolutely not my intent.
It is quite easy, if a relationship is your first, or you had flings or terrible relationships previously, to be in a relationship where you would declare yourself as happy, and to the outside world you might seem a good match.
But sometimes in these relationships, because you have little context for what's 'good' or the person you are with has conditioned you into thinking certain things are normal, you are a boiled frog, and it's only once you are free that you can look back and go 'I would describe myself as happy, because when things were good, they were very good, but I had no access to joint money without questioning, he would fly off the handle at minor things, and he left all the housework and parenting to me'
And I wonder how many of these age gap relationships fall into this category.
Because it also happens with same age couples. I know of at least two couples who have been together since university, who would describe themselves as happy, yet in one the husband actively despises the wife, and shuts her down constantly, and talks down to her, and she has developed exagerrating illness as a coping mechanism because that's the only time he eases up on her. The other, they argue constantly and think anyone in a relationship who doesn't is weird. Now a lot of people might read that and say 'but if they think they are happy, then what's the harm, if they don't know any different, other people don't get to dictate happiness'
Which is a fair point, but anyone whose ever suffered with chronic stress, or a bad relationship, knows the toll it can take on your health long term. Never mind the fact that these relationships often produce children who look to their parents relationship model, so in fact, there is a 'harm'. But also often these relationships can entail financial control and abuse, because 'he's better at the money side' and suddenly he's run off with a 21 year old from his work and she's posting on here saying 'he was older and good with money, so he dealt with everything so I have nothing' - you see it all the time. It was good, until it wasn't. And no, as I've just explained, not exclusive to age gap relationships. But the risk of a power imbalance, or one person subconsciously taking the standard that the other person sets as 'normal' as part of relationships and being unable to know what's normal ups and downs and what is something more sinister, is more heightened when one person just has more life experience than the other.