I have a set of pre production LNPA 150 monoblocks in the living room that are used for the "entertainment center" that are now 15 years old, so this summer I decided to re-cap them as the electrolytic caps are now closing in on the end of their life cycle. Both monoblocks were working just fine before the project started.
After a thorough cleaning out of assorted dust , dirt and cobwebs, I replaced all of the electrolytic caps with Sprague electrolytics and updated the units to the my last set of changes. (these are very minor changes) I observed that as I brought them back up the amps had maintained the pre set voltages and currents I set close to 15 years ago. There was damn little, if any, drift over time. Try that with a 15 year old tube amp!
For those if you with aging solid state units, You may wish to consider doing what I have done because the price to replace the caps in both monoblocks was about $150.00 including shipping. The price of the Windex cleaner, Isopropyl Alcohol, and paper towels used is really marginal so I will not consider that as part of the overall expense.
I hope that 15 years from now I will be alive and able to post something like this again, because no one really knows just how long transistors last if you keep them inside of their specified ranges.
d.b.