It's funny to hear younger folks react when you tell them you use tubes...
I've been a tube guy for most of my life, built my own 6L6 based power amp back in the late 70's. All my guitar amps are tubes (Fender and Marshall), never played a SS guitar amp I liked.
My audio tube gear started with an ST-70 many years ago. Cleaned it up, replaced the selenium rectifier and a few caps and it sung well. Had an Audio Research tube integrated for a while. Found a pair of Mk 3's that had ben 80% restored (re-capped, new chrome on the chassis, xformers painted and other goodies), I finished the job and they looked stunning. I happened to be talking to a guy in my local shop one day about them, it turned out he was the guy who did the 80% and then sold them to the guy I bought them from. He immediately asked me to buy them back and made me a great offer. I didn't have the heart to keep them, so I sold them back to him. They ran well, but didn't really work well with the Totem Arros I had at the time.
My current audio system amp is an AR VT-100, which is built like a tank and sounds awesome.
In all that time, I have never had a tube go bad on it's own. I've had very old amps pop their caps on startup (I didn't use a variac to bring them up), but never actually has a tube go bad. Maybe I'm hugely lucky (can't tell you how many times I've rolled 12 ax/at/7025s in and out of guitar amps.
BTW Legrace, I like what you're doing with SS for low and tubes for hf. I was considering something like that for my video system, but was a little concerned about the on/off cycles of the everyday use of the video system, which is why I went SS. Hmm, now you got me thinking about maybe swapping out the main channel amps for something with bottles...
Tubes are generally very reliable, I'm a little surprised you had KT88's crack - what brand was it?
Main: JMLab Mezzo Utopias, Oracle Delphi Mk 1/6, SME V, Koetsu Urushi Vermillion, AR Ref3, AR Ref Phono2 SE, AR Ref-75, AR CD3, Sec / LR: Rega P6/RB2K Lim Iso base, Acrylic skeletal plinth/braces, dbl pulley, gt sub, Sum Celebration, Anthem AVM60, Krell 402e, Totem Mani-2, 2X Anthem MCA50, PH-1