is this a retorical question?
Well I'd say too many is when
your taking out loans for your next plane
your building a second 2 car garage to store more model or your renting out a storage slot for youe current models and need another for more. at that point maybe you have a few too many. until then, you don't have enough. Just on the next plane do something differant, like a thermal glider or something you normally wouldn't do