Deteriorating speakers -- Class A today, C Tomorr

I have never been able to find an article adressing the aging of speaker cones -- a'la long term road test -- to see if the sound after the break-in period deteriorates over the years. This is of great importance to me because speakers that I lusted for 2-5 years ago are now appearing on the used market for prices I can afford.

Can any tell me if a speaker such a the Jmlab Utopia, Wilson Maxx, etc., sound as good after years of usage, or is the reason that the upgrade addiction sets in is to offset the aging speaker cones.