Preventive maintenance or wait till it breaks?


This is more focused on older gear- do you run gear until it's showing obvious signs of problems or do you do preventive maintenance before problems appear? I fall into the preventive maintenance side as I replace capacitors that are 20 or more years old. 
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I am fortunate- I do have access to top notch niche technicians. For instance- I live relatively close to Audio Classics and they are my go to for Mac service 

I will only use top people specialized in the gear that I want work on 
Here is my list of questions:

  • How long am I going to keep it?
  • Sources and preamps are cheaper to repair and less likely to fail catastrophically.
  • Amps are more likely to take out speakers, as well as have transistors which are no longer made.
  • Was the gear built before 2000? Caps since then are more reliable (I have no strong evidence of this though, just my impression based on overall improvements in electrolytic capacitors).

Best,

E