I am very happy with my 75SE, which has been upgraded to SE status for at least 3 years. I haven't replaced the tubes and have no idea how many hours they have on the clock. I listen a lot to my Stax l700 ear speakers anyway, so don't believe I am over 2000 hours.
I have to say that the numerous stories of damage when a tube blows, do concern me. Are there any other clues to near failure, such as wandering bias? It would be nice to change them just before one blows. My amp only has 4 tubes, but they are still costly when you have retired.