A point in ones life which takes place after the normal adult stage and before the "always has a bowl of expired werthers originals" stage in which a person is grumpy and unpleased all the time

Adj. Something that is expected to have a long lifespan by virtue of having existed for a long time, based on the lindy effect, named for the New York restaurant Lindy's, coined by Albert Goldman and popularized by Nassim Taleb.