Having personally met almost all of the "major players" at Rogue Audio at the big audio shows (Mark, Nick, Bill and the gang), and having talked to them frequently on the phone over the last decade- I can say, this is a company populated by a bunch of stand-up guys. They are true "gearheads" who love to build great stuff, and are very good about before- and after-the-sale support.
AFAIK, they still support every amp they've ever built. They've been building amps for over two decades now, and I have yet to see a dud model from them (in terms of sound or durability), as well. Some of the early models can do well with upgrades (i.e, like upgrading an earlier Cronus from EL34s or KT90s, to KT120s- that's a good idea), but they support those things as well, with all the parts needed. Upgrades aren't "dirt-cheap"- but the prices, IMHO, are fair, for what they do. You can even have major upgrades done- for example, an early M120 monoblock upgraded up to a modern M180 Magnum- it's a couple grand to do that, but you get what are effectively the same as their $6000 amps now...
As for tube pricing- IIRC, replacement KT120s from Rogue Audio, are about $60 or so each, plus or minus a bit. You can buy from one tube, to as many as you want in a set. Smaller tubes are primarily 12AU7s and 12AX7s in most models, with a few models that use 6H30P tubes too, and some models that use 6SN7s here and there too. All easily available from Rogue, or from myriad other sources.
Regards,
Gordon.
