Power Amplifier Longevity

With quality gear well worth rebuilding 
the capacitors dry out ,
and while rebuilding improve  the design ,most all amplifiers or preamps 
use good reliable average parts ,coupling capacitors many good brands ,for the power supply  there to buy the best electro Lytics , get all1% resistors 
and signal path small values Vishay naked, Non magnetic Tantalum resistors brings natural character in the right areas. And for sure rewire 
Neotech makes excellent Teflon -0 Crystal copper wiring,as well as silver.
your connectors for sure make a difference ,for not much money 
WBT makes a less expensive all Gold Copper text gen for speaker terminals 
and rca, Furutech makes the best gold
or rhodium over copper IEC inputs 
from there there are many tweaks .

No AV piece made more than a couple years ago is a good bet for longevity (excepting Theta Digital)

I am a big fan of Theta, lived very happily with a Casanova for years. Really should not have sold it. Anyway...

Sadly, since HDMI came out, Theta has usually lagged the industry by years. I always worry it’s on the brink of financial collapse. It took what, like 3 years for them to introduce an HDMI ready processor?

I wish this was not true. I was really ready to buy the new Casanova. Supernova? Something like that. << sigh >>

At least relatively, the MRX 720 will be cheaper to replace than a Casablanca will be to upgrade. :)

My Classe DR3 is 40 years old of Pure 25w in Class A and works real good ;)

These are typically the factors that reduce any electronic device’s life:

1) Inrush current at turn on.
2) Temperature.
3) AC voltage spikes which causes the maximum allowable voltages to exceed for various components.

Sooooo.. pick an amp which:

1) Has an inrush current limiter (lights do not dim when you switch your device on).
2) Runs cool.
3) Components in it are rated at twice the maximum rated operating voltages.

Pass labs seems to be one of the the few exceptions where most run pretty hot (class A) and yet still are very reliable. I can only guess that they must be using absolutely superb components inside (like 105 degree C capacitors) , which may also explain their prices.

You people are a bit confused. Full of hyperbole, misinformation and bad advice. And I swear a few of you have as well, bad intentions. 
 I am sure at least a few of you will disagree. But your arguments are devoid of ANY, "actual", facts. It is "Heresey", at best, and even that's a stretch!
    Caps? What? Are they suddenly evil? Has ANYONE commenting here ever replaced a capacitor in ANYTHING? Doing it themselves OR even paying to have it done?
 Brian, Do not listen to all the Malarky, Please.
How long is an quality capacitor designed to last for? Why oh why, does everyone that has simply owned more than one decent amp think they understand electronics?

 For instance....The comment above? See #1, 2 and 3 on his "Amp check off list". He has not the foggiest notion of what he is saying. 
1, You CANNOT purchase any electrical device in the USA that does not have either an IR limiter, "The common BUS, Fuse is one type". OR IR limiting is designed into it! .It would be otherwise illegal to sell! "Per any version of the NEC"!
2, Runs cool???? Please feel free to email Nelson Pass that please. "He could use the laugh". That's about the funniest thing I have heard from someone claiming to understand rudimentary modern amplification.
3, Um......Ha ha ha ha ha, Yeah, "We tend to do better than one,  automatically"!. "That would be during the design phase of a product".
     Get my point Brain?
I currently own more Nelson Pass, designed amps than will even fit in a 12' x 12' room in my home. And I am about to put a bunch up for sale.
 I guess no one here talking about Pass amps has ever noticed that nearly ALL of them have "NO", ext. heat venting whatsoever. Heat is your friend in that type of amp architecture. The largest 2-channel he ever designed? I JUST sold mine. An orig. "X-350". It NEVER ran hot. "Surface's never above 118 degree's F."...And if it is ever re-capped? It will sound like crap and probably "begin", to run hot.
 My "Aleph 0", mono-blocks from Pass Lab's did run hot. Maybe because they were attached to the worlds largest transducers playing down, down, down to "Who knows where". But those, "Theoretically". Will double down the ohm load into infinity anyways. OR at least until they melt. "Did that once".
Caps dry out because they have burst. They leak when that happens. They burst because of misuse. Not really from age. "The capacitors built in Mason Jars, and over 100years old from the workshop of Mr. Tesla are still, NOT dry". We are still using his basic design for caps. "Except for the new super caps", "Another story"..
 There is no need to replace nearly any, modern made "Electrolytic" Capacitor manufactured in the last 30-35 years, unless the amp has failed.  Why would one fail, "cap"? Usually either a bad design of cap OR amp. And nearly always they have also been abused. "Like doubling or even quadrupling the Ohm load against the intended design. By NOT hooking it up correctly! By hooking every single component you have, "Plus a few lamps, a fan and a clock". To a single residential 15 amp circuit in which the service breaker that was past it's prime a quarter century ago.....doth reside.
  If you have good gear. Especially amplifiers. Have it fully serviced AT LEAST every five years. Every two if you smoke. Good gear will last you a lifetime IF you take care of it. I have tube amps from the early '50s with the orig. tubes that still sound and run great!
 And If you would like to try one or three of the amps I mentioned above? Let me know and we will work something out. And ALL are recently serviced, guaranteed and warrantied. BY ME! and most are in your price rage I believe. "I should tell you though, I am not a dealer. I am a collector", And a small manufacturer.
You will get out of this hobby what you put into it......Good service is not cheap and depending,. May be impossible to find locally. But there are a "Plethora", Of good shops. Most small, That will do this through Mail-Order. And plan to spend a minimum of $250 having it done. Not counting shipping if you go that route.
 Finally,  "IF, someone say's they will fully service an amp for $50? And it's not a blood relative you trust? Run....."
     Still with me Brian?