When DS was first born, he'd never stop nursing, and I couldn't tell if he was actively sucking or not; I'd cut him off at 20 minutes per side. When he got older, he'd start detaching himself.
If the baby's sucks become more shallow and sucking less frequent, he/she may be done. Our IBCLC encouraged us to tickle her on her ear or back to keep her eating actively so she wouldn't get in the habit of leisurely feedings and comfort nursing. (My nips were seriously torn up, so I couldn't handle having her on the breast any longer than necessary.)
He's 3 weeks old. I try to keep him awake so he'll feed well and I reoffer whenever I burp him or he detaches, but usually when he detaches he's asleep. So I always worry when he hasn't passed out that he hasn't eaten enough/my breasts aren't supplying him with enough.
Re: Full?
When DS was first born, he'd never stop nursing, and I couldn't tell if he was actively sucking or not; I'd cut him off at 20 minutes per side. When he got older, he'd start detaching himself.
Natural M/C at 8 wks December 2009
DD1 born October 2010
DD2 born May 2014