Micro socialising sometimes equals macro problems

I was having lunch with a straight friend of mine today and was updating her on my life and social circle. I told a story about the ex of mine who goes on holiday with her ex and whose ex is now dating an ex friend of theirs (when they were a couple). "Ho boy!' was the reply. This is an old dialogue between us. My friend seems to think that lesbians cannot let go of their old flames. She feels we move from friend to partner to ex and then back to socialising together. She told me many years ago that once straights break up they quit seeing one another, period. Well, unless they happen to bump into one another in the Woolies aisle or at the Home Affairs offices. She has a point.
Several lesbians I know have, at one point, continued to live with their exes (even the ones who had cheated on them). They become roomies. Now I can understand the financial imperatives behind that but come on... roomies? Rather run into the middle of a dual-carriageway and throw yourself in front of a Putco bus. At least the agony will be over soon enough.
Other friends socialise in groups with numerous exes. Take another gay friend. Her partner used to date my ex. She used to date someone who is an ex of my ex. SA is small, we all know that, and so it's often impossible to avoid bumping into an ex socially, but many do it because they want to. What's that about?
Look, there are advantages. You don’t have to repeat stories, for example. Everyone knows them. They’ve either heard first hand from you, or second hand from one of your exes, or an exes ex. It’s all very straight forward, if you’re gay.
So, what’s your take on this? Madness disguised as normality? Necessity in these times when the pool is a-shrinking? Or just wonderfully illustrative of how loving and forgiving women are?