Are Lamm preamps hard on tubes?

Put the stockers back in and give it a test. 5-10,000 hours isn't uncommon. If a tube (valve ) test as balanced, at 90-110% and low noise, that is what it is. No need to guess. When Brent Jessie says "this is the test results", it doesn't mater what anybody calls it.. NIB, NOS, NEW, USED, PULLS..

Pull and reseat the valves first, and listen.  After that, swap to the old if the sound sound is still off. 

No way to test for balance, so wing it, roll to the originals.. What ya hear?

Make sure all the connections are clean and tight.. Give all the drivers a close listen.. Make sure all the drivers are firing..

I got nothing else that is cost free... Happy hunting..

Wash out those ears too.. ;-)

Regards

There are plenty of Russian tubes made before the fall of the Soviet Union. These are indeed NOS! Certainly cheaper than expensive hyped - and used! - Mullards and Tele's!

How would you know if they are true nos tubes or used that measure as nos?

Are Lamm preamps hard on tubes?

No

@jasonbourne52--some of the older Russian tubes like the DR Reflector 6h30 are now quite scarce, and often late production which is not, as I understand it, comparable to the earlier tubes (circa the '70s) that I use. They are now quite pricey.
@invalid- aside from a reliable vendor, there's indicia, from how the tube itself looks, to how it is wrapped and packaged. Some (keep in mind my tube knowledge is not deep, just long used tubes) were sold in bulk and that packaging is sometimes shown. 
I would also hazard that some truly unused tubes could suffer premature failure, but I've had pretty good experience with vintage tubes.
Good luck-- it's a jungle out there.