In an earlier post I mentioned I had owned the EML XLS tubes for 7 or 8 years. I came across an old post of mine regarding 300b choices. At the time I made that post I had owned the EML tubes for about six months, so early spring 2013. I still have those tubes and they still sound terrific! They tested strong 6 months ago on my friend’s Amplitrex tube tester. My how time flies.😊
Rlowe,
It’s hard to say, I used the Shuguang BT heavily for 2 1/2 years prior to getting the Takatsuki 1 1/2 years ago. The BTs are still very usable presently. I have the AVVT 32b (300b) which the Manufacturer said is a 40, 000 hour tube! I also have the EML XLS which shares a similar design and pedigree so who really knows?
Charles,