I have a CAT SL1 Signature preamp that I have been using every day for the past 28 years. Couple of years ago I measured the caps and all were to spec for micofarads and ESR.
So the answer is... it depends. But for the most part, preamps do not generate heat so the components spend their lives in their design 25C ambient air temperature, which makes them very relaxed and stress-free.
Before you buy an old preamp (or any other piece of equipment) one big concern is that some parts may no longer be manufactured. Toshiba had a lot of good transistors and current source jfets in the 80's and 90's that were retired in the early 2000's. So be careful poking around inside -- damage one of those semis and it cannot be replaced.
So the answer is... it depends. But for the most part, preamps do not generate heat so the components spend their lives in their design 25C ambient air temperature, which makes them very relaxed and stress-free.
Before you buy an old preamp (or any other piece of equipment) one big concern is that some parts may no longer be manufactured. Toshiba had a lot of good transistors and current source jfets in the 80's and 90's that were retired in the early 2000's. So be careful poking around inside -- damage one of those semis and it cannot be replaced.