Do people really care if Carl looks older between seasons? I don't think so.
I do. If time has only progressed 6 months and he's 25 now but being treated as a 12 year old its just not going to work. That's often why kids aren't on time sensitive shows or they get rid of them early on (ie Walt on LOST). Carl is THE reason time is progressing so much between seasons.
That said, I'd love to see a winter season. It would give us a nice break from all of the sweat