5687 tube


I have a couple of questions about the 5687 tube:

1) What is the approximate life span of this tube? They run extremely hot, making me think they may have a shorter life span.

2) How important is this tube to the sound of the component? For example, my amp uses 2 5687s, 6 6922s, and 8 KT88s. In terms of bang-for-the-buck, where would you put your money? Into the 5687s, 6922s, or 6550/KT88s?

3) Does anyone have some info about various 5687 tubes and their relative merits in high-end applications? I currently use a Raytheon JAN 5687 in my amp.

Thanks in advance.

Tom
tfkaudio
Thanks for the responses. My gear is a Sonic Frontiers Power 2 amplifier. Would you say that the 5687 tube quality is critical for this application? Or would money be better spent on the 6922 and KT88 tubes?
Seeing as how 5687 are the cheapest tube type you're using, it wouldn't hurt to invest in a pair or two. Six 6922 and four KT88 will cost you A LOT more then any two 5687 can (except for the Sylvania gold brand and the commonly substituted 6900). I suspect the 5687 is the first stage gain driver in your amp, so it might make a meaningful difference. But as I said, the Raytheon you're now using is a nice tube, and unless it's aging, your money might be better spent elsewhere.
I've also heard that a 7119 tube might also provide excellent results.
Thanks for all the responses!

Tom