Primaluna?

Prima Luna is good stuff and priced well. Auto bias is nice but biasing tubes is not that hard. On the question of tube life, except for infant death, if you have some hours on your power tubes and one fails it's probably better to replace the whole set. I've never had an issue that required the protective tube system to activate. I have blown tubes on other amps but I have not needed anything other than a new tube.

PL is a good starting point.

Like tires on a car one is bad I replace them all.

My first edition, entry-level Prologue One integrated essentially put me out of the need/want-a-better-amp game. In the ten (fifteen? who knows?) years I've had it, I've probably gone through a good dozen tubes, but by and large the device has been the most reliable piece of amplification I've owned. When a tube fails or you just want to refresh the bunch, you call up Upscale Audio and let them guide you in the selection for the replacement(s). Think of them as wine stewards at a fine restaurant. I'm not a guy who changes speakers on a whim, and I'm pretty sure I went directly from Celestion SL600s to my current NOLA Boxers, and the sound is balanced, mellifluous and ballsy enough to keep me from dreaming of Krells. (I'm just a classical kind of guy even if I do listen (and once played) my share of hard-hitting rock. The amp is three-dimensional as hell. Every once in a blue moon I remove the bottom of the device and lubricate the volume and selector knobs (they'll eventually get noisy), Other parts have failed over the centuries, too, but bottom line, I'm happy as a clam with my PrimaLuna. It's enabled me to put my music-oriented money elsewhere, e.g., a brace of violins. True, I don't think I've ever played my stereo above 85 or so dB, but all in all I can heartily recommend the brand.