I often also think about this in the lead up to meeting my little jnr!

I have no family near me (nearest is 800km away) lol so dont really have the worry about people at my doorstep but i assume that when we visit that they will want me to leave bub with them and 'go out' as such... which is think is a very personal choice if you want to go out or not...
I mean i am having a baby to be a mum not to be able to go through labour and go to the pub on my own! :P

I know my MIL is very full on with her current grandson and this is something i think needs to be recognised by everyone when accepting babysitting.

My SIL liked having MIL look after bub (still does 3-4 full days a week) but when SIL wants bub at home when she had days off and if these days fell on the days MIL usually had bub then MIL got very upset that she didnt get bub that day.

I keep this in mind for the future... (i know it is kinda the opposite of what is happening in your case Emma but if you find that you like the babysitter and use them all the time when you decide you dont want the babysitter anymore they can get too attached to the baby and have 'withdrawls' as such.... sounds a little strange.

But it is even stranger (and a bit sad) to watch.

Sorry for going off the track but it is something regarding babysitting that i think about....