I have three girls, and this is my belief: If early-on they get used to falling asleep on the breast, or while being rocked, or bounced or whatever, then that is what they will need to get to sleep from then on unless you retrain them (which sometimes doesn't even seem possible!). My first would fall asleep at the breast, and thereafter always needed boob to get to sleep (or back to sleep if she woke in the night). I weaned her at 1 year old but she never slept all the way through the night until she was 4. She always needed skin-to-skin contact to get back to sleep, instead of self-soothing back to sleep.
I tried to do it differently with my 2nd daughter, and put her in her bassinet/crib while still awake, so she could learn to get herself to sleep and not associate boob or skin-to-skin contact with falling asleep. BUT... I would fall asleep with her in the bed with me while nursing in a side-lie position. So she, too, got used to falling asleep while breastfeeding. The same issues have resulted. She's now 2 and doesn't sleep through the night.
On to DD3, who is 8 weeks. I work very hard to put her in her bassinet while still awake. When I do this, she DOES drift off to sleep by herself! (I sometimes do lie down and fall asleep while breastfeeding, though -- I try to only breastfeed sitting up so it doesn't happen but it's hard!) I really believe this is going to be the one who sleeps well because she will not associate falling asleep with having mommy touching her or having the breast as she drifts off.
I know a lot of women cosleep and feed off and on all night -- which is basically what I ended up doing with my first 2. I am sooooo tired of having little ones in the bed with me and DH all the time. I want one of those kids who drifts off to sleep in their own space and sleeps through the night this time!