@roxy1927 I had to sell off a few beloved 20+ year old Class A/AB SS amps for scrap parts because the boards were deteriorating and no longer available. Gave up after 2-3 board repairs, traces going bad, cracks from heat. Roll the dice. Some of the top manufactures back their products after 10+ years, yet rare.
Over 20yrs old, plan on buying a 2nd one for spare parts or pick a good one backed by someone like Bryston, ARC, Pass, who may actually help you when needed with some kind of guarantee it will last more than a few years more. If not, simply consider it a throw-away, and this is an option some take.