Most skis after about 100 days don't ski quite the same as when new. Edge hold would be the most noticeable drop off in performance due to materials wearing out and flex and torsional stiffness going soft. Volkl skis used to be more costly than other brands but were famous for longevity. Now that K2 owns Volkl I don't know about the longevity.
Foam core skis, especially with a heavy skier, wear out the quickest. Skis with a double torsion box core and metal layer are the strongest type of construction and usually last the longest.
My Volkl Snow Rangers with 300+ days on them still ski like new, but they are lots of work to ski them compared to today's modern powder/crud skis.