Life span of tubes?


Has anybody experiences with KT88's' life span? I run an McIntosh MC 2000 about 6 hours a day average. When do I have to worry about the tubes?
What happens first when a tube indicates it won't go on much longer?
aida_w
Rcprince is right of course. Haven't seen any NOS Gold Lions or Monarchs for quite a while. Occasionly you can find one or two used at Billington's in the UK and they cost lots of Sterling. To get a feel for prices of other tubes, I suggest you check Ebay regularly to get a feel how the market is.
Detlof, that's because I'm hoarding over 50 of them! Told you I had a lifetime supply......
Lucky you Rcprince and a long, long life to you and your tubes of course ! (-: