How long can I expect tubes to last on a preamp or MW CD player?

Secondly, what would be the signs of tube deterioration?  Without a tube tester, is there any way to tell how much life they have left short of they aren't working anymore?  I have 7 tubes between the TRL DUDE and MW 5400 Signature Truth.  I may have hit that point on at least a couple tubes.  Seems to have dropped a little in SQ.  The 2 SNL7 tubes on the MW are only a couple months old.  The rest have been on 24/7 for at least half of their lifespan, about 4-5 years with NOS tubes in them.  I still have the original tubes with very little use.

you don't want to leave tube gear on 24-7

yes i think some of your tubes, based on your description, can stand replacement - when you get new ones, see if the sound improves, then you will know

Thanks for the replies jjss49 and noromance.  Sounds like I'm well over.  The PPT stuff made such a difference in performance, I didn't notice the drop-off in SQ until this past week.