amplifier longevity

Half of this makes no sense.
I scratched out the part that does make sense.

I traded them in for a set of Class D monoblocks 3 years later because I couldn't stand the heat and the tube maintenance. 

At 10 years old they ran like champions and had not one issue.  

But here we agree and have experienced the same.

Not counting my first tube amp, a VTL..... …

My mid 1980's Acoustat TNT200's worked when I purchased them last year. I just had them rebuilt and modified by Roy Esposito, a former Acoustat Engineer. They worked 35+ years before I had them rebuilt.  I suspect they will outlast me...

+1 @cakyol 

Another thing to consider: if you are like me, sometimes you want to play a record or two for a relatively short listening session. Since SS amps can (and should) be left on all the time, they sound optimal much more quickly than tube amps that you can't leave on all the time, and the turning on an off frequently can wear out the parts.

If you like to monkey around and roll tubes and are more of an equipment head than a music head, tubes may be for you. If you are like me and want to KISS, go with a high quality SS integrated amp. Luxman is excellent and there may some others that are of better value to consider.

Since SS amps can (and should) be left on all the time

So why do they put a power switch on the amplifiers?

Many companies are now putting them on the back of the unit. If you are not going to be using it for an extended period of time,they should be turned off from an electrical safety standpoint.

some very low current preamps or phono stages dont have power switches.