How many November babies are still in infant car seats?

We are planning on making the switch at least by 12 months old but I'm wondering if we should do it sooner? He still fits of course, 20 lbs and infant seat is good up to 35 but I've been reading that convertible is safer because it protects the head more and may be more comfortable for them. But our stroller is a travel set, so I hate to switch and then not be able to just pop him in the stroller like i do now. We walk everyday. I also still carry him in the car seat occasionally if he's still sleeping. Is it okay to wait until a year old or is it much safer to just switch now?