I'm a touch old fashioned about these things, and so my own outlook sympathises with your take on this, Peason. In the long cold decades before Facebook, I felt uncomfortable at my new husband hoarding photos of his several-relations-back 'serious girlfriend'. We spoke about this and it was clear he saw no reason why these were any of my concern, or why I should be upset by his numerous references to her in conversations.
In other words, he wasn't over her, and it was casting a shadow over our present time together.
Respect to all other posters who managed, but for me love is a totalitarian state that will allow no potentially rival parties to exist.
We have been together for 36 years. The photos 'got lost' during a house move, 33 yrs ago. Ahem.
But this is hard to control with social networking, and I don't know how I could have coped.
I agree with you on an important point, which is why on earth should a man you are living with spend ages on what is effectively a separate social life? Doesn't matter which way you dress it up, it comes down to the same, which is he's chummy with a woman he has slept with.
But I'm old-fashioned and probably wrong.