Lifespan of amps and preamps?

I've encountered many 40 to 50-year-old electrolytic caps that test within spec and perform their intended function. Any half-way decent cap will last 20+ years if the associated circuit and its heat dissipation are competent. 

People like to believe they hear dramatic differences when they swap power cables and it's most likely the same phenomenon that occurs when they have gear recapped, i.e. placebo.

If your gear sounds good, it's good. 

If you decide to go digital, keep your old system.  My 39 year old B&W's and old  Adcom amp sound fine with my television.  My "new" system sounds better, but it has 1980's Audire electronics and 1990'd B&W's. Recently, I auditioned some really expensive integrated amps on current B&W speakers, because I know their qualities.  I did not hear anything digital that I would be at all happy with, but that doe snot keep me from listening to my jazz channel on XM radio. 

I am going to have an interesting experience.  I am super busy right now and don't have a lot of time to devote to a new system.  But I really wanted sound in my office.  So...  I ordered a Peachtree Nova65Se and a pair of Focal 906 speakers for my office.  It will be interesting to compare the sound of this setup with my older equipment. 

Maybe the old stuff will not sound so great after all. 

Scott.

Lots of great stuff in this thread, but for me the best was OP’s original post and how he talked about the components and how it was a big deal to buy all of them as a 20 yr old kid in 1990.
Damn right it was a big deal! I remember looking at all of those pieces in 1990 and wishing there was some way I could replace the Pioneer speakers and Kenwood receiver and CD player that I had with gear of that quality. In fact, had I been able to, I might have gone with those exact components that OP did. Good memories.
When I finally could afford to upgrade in 2000, I did go with B&W and NAD!  The NAD passed on (remote broke and no longer handled current HT formats) but still use the B&W’s as front stage of main home theater setup. 

Getting a new system for the new office seems like a good way to enjoy what you have while trying a new direction. Also could be an opportunity, when you get the time, to experiment back and forth and mix things around a bit.
While I am now using an Integrated Rogue tube amp, driving my little Maggie 1.7s, I still have and love my old Audible Illusions tube pre amp and trusty old ADCOM power amp. I had to rotate them back in a while back, while waiting for a new set of tubes for the Rogue and was amazed at how good they still sounded. Regardless of what gear I pick up in the future I will never get rid of either, the AI pre amp or the ADCOM. They’re worth more to me than what I would get from selling.
Enjoy the merits of both your old and your new systems.....Jim