I know for us about an hour tops, sometimes as little as 45 minutes.
If you think about character buffets, being a buffet you have instant access to the food, don't have to wait for them to cook it and serve it to you. So that shaves off a bit of time!
Only issues can run into would be if characters moving slowly to get to your table, and then waiting for that last character to come around. Still, I think we're always out within an hour. Park Fare I think we take a tiny bit longer in, just really enjoy it there and we keep going back for more and more food!
Cape May breakfast the characters seem to come around fairly quick I thought - one time were out of there in a half hour.
I usually budget time-wise an hour and fifteen per character meal - and that is to include the time we check in and then wait to get seated.
Only thing that usually keeps us there longer than we plan - is waiting for the darn check! I like to ask for it before we're finished. Had a lousy server one time at Akershus for lunch last trip - asked for check when she brought out our entrees, told her we weren't going to be having dessert. Table seated next to us, sat at same time as us, got entrees same time as us pretty much.... they got dessert, finished their dessert and were out of there before we got the check. was fuming - and yes, struggling with autistic child and needed to get outta there. Asked her three times for the check and stressed we HAD to get moving out of there.