Recently my baby (3 mos.) has been nursing for extended periods of time.. 30-40 mins when prior to this he would only take 10-15. He will fall asleep at the breast and just suck on me like a pacifier. If I let him, he would go on for who knows how long!

At what point do I remove him from the breast? When he starts slowing down, should I offer him

the other breast- even though milk is still coming out of the breast he is nursing from? Any idea why he might be doing this? He is definitely gaining weight so I don’t think it’s a supply issue, but I could be wrong!