our situation is like Heaven's - we dont exclusively co-sleep - if DD is settled, she stays in her cot. if she goes off to sleep and i'm still awake after a night time feed, i'll pop her back in her cot (in our room) so that i can cuddle DH. it works for us though. i lay down to feed her at night time - we are both more relaxed (i have a dodgy arm, so holding her for long periods gets painful, i can't relax properly, and she picks up on that) and it means we both get to sleep and/or rest better. nights like last night, we NEEDED to co-sleep for me to get any rest. DD is going through a wonder week, a bit of a growth spurt AND teething - so she's not sleeping very well. in the six hours from midnight to 6am, i counted 8 full wake ups - and she attached herself another three or four times. if i got out of bed and tried to feed and settle her each time, i'd be a zombie.

i don't personally feel there is anything wrong with co-sleeping. i used to wonder why people would do it - but i changed my mind because it works for us. DD sleeps better if she is feeling off color. we sleep better. we are very close. i don't want her to feel neglected.

as to what would happen if we have another - well, that's a big IF for us, however, you have at least 6 months to work out ways to transition your child out of your bed if you need to. six months makes a HUGE difference in a childs development and their emotional needs. there is no need for it to seem like they are being abandoned. in the same way you wean them onto solids and less BM/formula, you can wean them off co-sleeping and into their own bed. it's not really a drama. i would never NOT allow DD into bed with us for cuddles and things if she is unwell though - even if we have another baby. we have another bed that we can use so that DH can snuggle her and me the bubba if both need us together, or vice verse.

everyone has their own levels of comfort though. there are many many people who won't engage in co-sleeping, who are more comfortable with having their child in their own bed. that's fine as well. as long as you are comfortable with what you're doing, then what everyone else is doing shouldn't impact you at all (but i understand your question was one of curiosity - and that's cool too!)