If I was building or refurbishing an amp for a customer, I would indeed want to make sure all the caps were reliable, again for at least several years without any issues. Also, I would shotgun replace all caps in anything over 20 years old. I haven't automatically done that in my own amps, but I feel you would owe it to your customer to give them something reliable. I have changed my opinion on this, as I have bought vintage amps with all the caps bad in the last year, and they looked fairly good visually, and one can cap created a nasty short that took out a fat node resistor prior to the fuse blowing. So I wouldn't play a Russian Roulette game with a customer's amp. Only my own !