Not going to pretend that I am a smoker who can tell subtle differences between a cigar that is 10 years old as opposed to 8 or 9 - I smoke to enjoy rather than analyse and never make notes so most comparisons are with general recollections from months before.
However, I still have Alex’s from 2014, various Hamlets (also 2014), Lopez Monsdales from 12 and 14, various Reynaldo’s (12 and 14), Yolandas from 12 and although they don’t all get an outing every year, to me, there has been no noticeable degradation to any. Some improved, to my mind, and some stayed pretty much on par with my recall from the year or two previous.
I also have a number of various size Johnny O’s from a few different years and they seem to have varied more with age imho - some improved whilst some got worse as one might expect.