Tube lifetimes.

[nightflameauto]

On the little DSL at least, it's cathode/self bias, so unless something goes horribly wrong it's not too big of a worry.

That's right - with cathode bias you could perhaps take an increasing idle noise level as an additional indicator of the tubes aging/drifting apart

Can confirm, definite noise at idle that wasn't there previously.

[ninjaraf]

My experience with tube life has been all over the place. I've had brand new tubes be dead immediately. Tubes last from weeks to years. I had a block letter 5150 with original tubes back in like 2010 that still worked, and that thing was played! Inconsistent at best. Don't think I've had a power amp tube failure, but I've had a TON of preamp tubes eat shit in 5150s over the years.

[Maddnotez]

Tubes will last longer than the robots after they takeover.

Seriously, while I rarely keep a single item longer than my socks I must say I have never once had a tube die on me.

I've had bad tubes from a brand new amp direct from the factory but never had a working tube fail from just being old.

[spawnofthesith]

I've never had a power tube fail on me, and can count on one hand the number of times I've needed to change a preamp tube out of necessity

In fairness, if an amp stays in my possession for more than 3 years its probably an outlier, but there's been some notable exceptions with long tenures. I also almost never buy amps new either though, so it's not like these amps always have fresh tubes in them either. The KT66s that were in the ENGL Thunder I was rocking for almost 3 years dated back to the early HCAF era IIRC