I ran a tube amp in my office system for about a year... Although that isn't a long time in terms of an audiophile's lifetime, I used the hell out of that amp. I bought it used, and after about 4 mos. I noticed a bit of softening of transients, and less extension in the high registers, so I replaced power tubes. Bam. Back to normal.
So while I may have not had optimal sound for a few weeks, it's pretty easy to hear when things "aren't right" and swap tubes around.
Besides, imagine being able to change the tone of your rig via changing out tubes: you WILL have more than one set, believe me
I wouldn't hesitate to buy a tube amp, really the maintenance isn't bad. It's fun to check bias and whatnot, gives you something to tweak and fiddle without buying things
The problem I have is my wife... Now that we have the rig downstairs in the main living space, she doesn't want to fool with tubes to watch TV. I just leave the power amp on all the time so she doesn't have to flip it on, etc. Obviously you couldn't do this with tubes, which have a finite lifetime.
I'm happy with my McCormack, it really does have the warmth and liquidity I loved about my tube amp, while also possessing serious bass extension and control, and more extended highs. No grain. I do miss the glow of tubes sometimes, tho, they're like little fake fireplaces
I think I'll keep the McCormack for a good while, and if I get the itch to buy tubes again I'm going whole hog and buying a pair of Cary 805C monos