Tube Life: 6SN7, 6DJ8, 12AT7 et al.

Most readings have nothing to do with a % over new. A new 12ax7 will read 90 on my SICO tester while a new EL34 will only ready 80. It's all relative. This 102 probably has nothing to do with 102% of life.

Most 12ax7's will last 5000 hours
6dj8's usually go 10,000 hours
12at7s fall in between

We've seen 6SN7s go 50,000 hours if they are NOS varieties. Our experience has been that of the modern 6SN7s (Chinese and Russian), that the Chinese tubes usually last longer, unless you have obtained some NOS Russian types made before about 1987.

The tube life depends heavily on the circuit in which they are used. So I would not rely exclusively on the nature of the tubes themselves- that would be over-generalization.

Thanks for your comments so far. I guess the real question is that if all parameters are equivalent, same tube tester, same amp, regardless of tube make or model, does the rate of decline tend to remain linear or does it increase with usage? If the rate increases will it do so even if the tube still specs at over NOS readings even if the original specs were higher? If again the rate tends to increase, is the rate of decline relative to the factory fresh readings or the NOS specification?

I hope I'm making myself clear, I think it's a very important question.

Thanks,