As to 100 years not being all that long.... not all that long ago they were walloped with an epidemic--- a fever that killed off a lot of the very old, and very young. (This will come up in the comic itself, eventually.) Most of the Elders are, in fact, more "Late-Middle-Agers." You will note that Gilder's fur hasn't even started to whiten yet. The current elders were little more than children when the Village was founded. (the Ennias Longscript notes, btw, should be regarded as having been written rather shortly after the founding of Freeman Downs.)
Besides which, 100 years is a long time to remember anything. Heck, 10 years is a long time to remember anything.