Haven't read the whole thread, but agree with WIckedWaterWitch.
I was encouraged my best friend (brilliant mother of 4, orgiansied, GP, lovely kids - I hate her ) to go out for dinner whe ds was 2 weeks old. Her view was the longer you leave it, the harder it will be. She is my guru on all matters childraising, as she is such a "together" lady, home cooks, walks the dog and her kids (ranging in age from 18 to 8) are all fantastic (did I mention I hate her )
I didn't go away for as long as a weekend when when ds was only 8 weeks, but I did go away for 9 days with dh when ds was 6 months old - having expressed enough to feed him for the 9 days, and expressing and storing while I was away (filled the chalet freezer!).
I enjoyed my time away - and I enjoyed seeing him when I got back
I don't think it is selfish to also look after yourself and not alwyas put the needs of the kids before your own. Personally, I think that that is not necessarily healthy - we still have needs as individuals as well as parents and you need to have a balance.
But I recongise that lots of people feel differently - and that some people almost physically cannot leave their children.