LinLai WE 300B or the LinLai Global Elite Permaloy 300B tubes ?

@sns 
"but then different equipment may affect tube life differently. So now I'm really confused!" 

This is true. Some 300b amplifiers are more gentle  (or tougher ) on the output tube than others. It depends on their chosen operational points (OP).  I know that my Coincident Frankenstein 300b SET mono blocks are a bit tougher on 300bs than some other amplifiers with more conservative OP parameters. 

This is one reason why the EML XLS has worked out so well for me. This is a very rugged and durable tube. After 5 years of heavy use in my amplifiers they were re- tested and the numbers had not changed hardly a trace from when tested brand new. Above all they sound superb in my amplifiers. Reportedly they have a 40,000 hour life span (I don't doubt this).

Caveat,  in my opinion some brands of 300b sound/match better in some amplifiers compared to others. Synergy is always a factor. 
Charles 

Yes...  There are a number of factors that affect tube-life.  Depending on the amp, some push the parameters to the limit, others are more gentle.  A testimony to EML if they can be used heavily for that long and still sound and test well !  I know with my BorderPatrol S20 EXD, the parameters aren't pushed to the limits, and I've had Sophia Princess mesh-plates last nearly that long.  I can tell though that the sound is not the same when putting new ones in and though the old ones still keep playing, there is definitely a notable sonic difference.  The tube loses dynamics, and sounds dull.  This is especially true of tube rectifiers !  

I've not been able to move past present Shuguang black treasures as PT in 300b mono blocks or as drivers in Coincident Turbo 845 because of warranty and durability questions. The Shuguangs expose every upgrade I've ever made in system, seem to be a decently high resolution tube. They're rugged, no failures ever over many years now, whats not to like.

Based on reviews and my experience upgrading various other signal and power tubes over the years I presume some of the tubes we're talking about would be an upgrade. Again, the EML and WE tubes seem to be the most durable, therefore, safest bet. LinLai Elite could be new top contender, I'd not expect any greater durability than Psvane. Recently I've been close to pulling trigger on EML, Charles, I know you've used the Shuguang in past, how would you compare it to EML? I'd expect higher resolution with the same modern sound as Shuguang. I'd hope for just a bit more romance, bloom in mids while keeping relatively tight bottom end. In fact, this is the exact sound qualities I'm looking for in any of the 300B's.
Does anyone else out there have direct experience comparing Shuguang Black Treasure to any of the other 300b tubes? As stated above, seeking a bit more mid range magic together with tight bottom end, wanting to stay in modern sound camp with just a bit more bloom and resolution.

@sns,
My Coincident Frankensteins MK II purchased in 2009 came with Electro Harmonix 300b, a very solid/decent sounding tube.

I replaced them with the Shuguang Black Treasure 300b. An immediately recognized improvement across the entire sonic spectrum. As you note very reliable and trouble free tube. Used them for about 3 years. When re-tested they were roughly 75% compared to brand new test measurements. Frankensteins were a bit hard on them (But near 7 hours 5- 6 days a week x 3 years). So yes heavy use.

Moved up to the Takasuki and simply better in every conceivable way. One failed after 2 years and replaced by Takasuki with no hassle at all.

Purchased EML XLS after 3 failures with the early generation Elrogs (Fortunately replaced under warranty).

Purchased the EML and zero problems going on over 6 years. Sonically superior to the very good Black Treasure (Dynamics both macro/micro, more extended frequency at either end, more resolution and inner detail) .
Also fuller body and richer tone, essentially more fleshed out (Like Takatsuki and Elrog).

In my opinion the more expensive EML XLS is definitely worth it compared to the Black Treasure. A higher tier 300b that competes with Takatsuki and the Elrog. Although the EML fits the "modern " sound category it has an organic aura, definitely not dry or sterile. I’d say that the Takasuki is more organic however the EML is organic enough😊, very natural sounding. In my system the emotionally engaging quality is absolutely present.

EML has a thick glass envelope and just feels solid and very well constructed when holding it in your hands. Bigger and heavier than the excellent Takatsuki. You can stick with the Black Treasure 300b and know you have a good quality tube. EML XLS is better at a higher cost.
Charles

Hi Charles,

I understand it must have been frustrating back then to experience all these failures. But that is more than 5 years ago and the tubes are now being manufactured under my lead longer than they had been in the old company. Would we still have the same issues we would not have survived that long. Maybe it is time to stop repeating that experience form the past.I think the last 5 years have proven that our tubes are not prone to failures anymore.

Best regards

Thomas