I always take about an hour at every character meal, but I usually see all of the characters by the time I'm done eating. At CRT, (at lunch,) I saw them all as I was eating my entree. At CP, two of the times I've eaten there I saw all of them while I was eating. The second time I ate there, (out of three times,) I saw Tigger and Piglet quickly, but Eeyore and Pooh took awhile to come around. That still took less then an hour though because I had an 8:05 ADR, and I was still out of the restaurant by rope drop. At LTT I saw them all while I was eating my entree, same at Garden Grill. At Akershus they seem to be spaced out better, but they still come out quickly enough, and while I'm eating.
For buffets and character meals you can figure an hour to an hour and a half for eating. For all other TS meals you can figure on an hour to two hours, if you order a full meal.