Carver 275 Crimson tube amp --- any feedback appreciated

Update after more time with this amp. I’ve been listening to the Bob Carver Crimson 275 with a Primaluna dialogue premium preamplifier for over  a month now. You can change up the sound with one 12ax7 tube roll or two12at7. The amp came biased at 100mA but the manual says you can adjust it down to 60mA for a softer more tube like sound and up to 120mA so it’s been a lot of fun experimenting with different sound. I found out I have one of 35 Crimson 275 made with a subwoofer switch, in which they dropped that feature because newbs mistakes and phone calls.  I like the subwoofer switch feature it frees up the amps power to 80hz and above. I’m glad I have one with this feature as I use a Velodyne Mini Vee sub for 80hz and below. I wouldn’t call the tubes cool but they are not blistering hot and you can touch them without getting burnt. I’m keeping it. Sounds great and a lot of fun changing up listening experience without buying new gear 

Bump for any more updates on the Carver 275 amp.

Can I get any idea of what the useful life is in hours on a set of tubes for the Crimson 275?