If they pull off, I will give bubs a back rub/burp, then stick them on the other side. Some nights they laze and will take awhile to feed, when they get older they get really efficient and draining those boobs! DD took one side at a time often, then would have both.

If I remember rightly bubs fed for up to 30mins each side in the early days, then got it down to about 10 on each side in a few months.