How do you know when to replace tubes

I am just a moderate tube user these days, but first thing I check for is any audible noise or hiss. Also if anything sounds unusually different in any way, tubes are one of the first suspects. I keep a few spares around so that I can a/b regression test individual tubes at a minimum and replace if not sure.

Noise is easy to identify but other sonic anaomolies not so much. A good quality tube tester like Atmasphere recommended is probably the only way to be sure. Not as common anymore these days, but depending on where you live, in lieu of owning and using a tube tester yourself, there might be shops nearby that keep a tube tester around and might be able to test them for you.

I would replace the two 6550 in the power supply after 2000 or 2500 hours. It is cheap insurance against the possible damage a blown power tube could do. The 6h30 tubes are not going to do any damage if one fails.

I also have a complete set of backup tubes for all my tube equipment. That way I always have a spare in case of failure.

BTW I own an Audio Research Ref CD7, Ref 110, LS27 and PH8

I find the comments very useful.I will follow Lostbears recommendation and replace the 6550 in the power supply.
Thanks for all the replies.

The only 6H30 tube rolling option I'm aware is 6H30-DR and they are expensive and tough to find plus you need 8.

Caveat Emptor buying 6H30-DR off Ebay located in Russia. I heard many received fakes.

There are rolling options on 6550. Since you only need one, you can try NOS TS, NOS GE ...

I believe your Einstein rolls 6922 so you got lots of options.

My experience is similar to Atmasphere, SQ gets softer as tube ages that will signal time to replace.

According to Kalvin @ARC, all power tubes (KT120 and 6550) regardless of position should be replaced @2000 and 6h30 @4000 hours in my amp so probably same as your pre.

I'm not taking any chances and replace all at the recommended intervals.

I say use your ears, and have backup tubes around from your god damn tube hoarding fetish...oops...got carried away there...there is NO way anybody else can suggest when to change the tubes on an amp they're not personally listening to so stick the backup tubes in as a reference when you suspect aging... I got about 8000 hours from a set of KT120s with great performance until I fired them (laid them off?) for getting soft, and until my KT150s arrive I'm enjoying the hell out of my backup 88s and 6550s. Note that all of this depends on how hard your amp drives these things, and power tube explosions aren't any more likely than SS amp failure...it happens, but rarely in well designed amps. I recently replaced my 12AX7s after rolling my various tubes around and found that my previous ones were also a bit dull...new set of Gold Lions put that right. This is the fun part of tube amps...love my Flashing Mullards...great band name...