Yep, my four month old is exactly the same. His daytime feeds are very short usually 5 minutes, sometimes 10/15. His bedtime his feed can go on and on. It's quite nice actually, he and his big brother have their bath, I put DS1 down, then I get a lovely snuggly hour with DS2 without having to worry about watching or chasing a full of beans two year old and DS2 gets an uninterrupted feed.