I think it can go up to any age, but it won't live to the age 300 :furawatchi: It'd die by then (unless, of course, there is a way to keep it alive that long..I doubt it)!
I think that tamas getting older depends on health and luck the same thing happened to me and one i forgot to feed and it didnt grow very fast. Well I might be wrong im not an expert i just started last year. On how old it can get i think it has to be healthy and u hafta be lucky
actually people, a tamagotchi can live up to over 100yr old. it can live up to a very long age if treated VERY good. like kyliesmum's tamagotchi,aaron, at over 120yr old.