Tube life in preamp. Please help

The best tubes for the various SP-9's are rare NOS that go now for $75 and up, each. They are getting rare!

I have used all of the SP-9 models for years.

These tubes can last 5000 to 10000 Hours.

ARC can still repair, and refurbish, to original state, all the SP-9's.

I liked the original MKI and the MKIII best. I did not like the MKII.

Buy a lifetime supply of NOS tubes, and do not leave the preamp on for days, when not listening.

You will be set for a lifetime of good sound!

I am running Audiovalve Challenger 180 monoblocks and Allnic L3000 pre amp and never leave them powered up 24/7.
When I know I am going to be listening to music the system gets turned on a couple of hours before use even knowing both units have standby capability. I really don't have a good reason other than I don't want to chance a hardware failure that could result in serious system damage or maybe cause a fire.
As far as tube life my pre amp tubes always seem to last for several years and if I am questioning a tube I test it on my B&K 747 tube tester.

"I liked the original MKI and the MKIII best. I did not like the MKII."

I was an ARC dealer for many years and have personally owned about a dozen different SP9 preamps. I keep going back to this unit because it really is a great preamp. I know others disagree, but I've had a massive amount of experience with these units and still find them wonderful.

I've had (2) MKI, (7) MKII and (3) MKIII.

IMHO, the MKII is the best. Just personal taste, but it seems to provide the best mix.

Can you describe the sp9 sand why you liked it best mofi?