I just passed the 1 year mark for my Elrog 300B tubes. I will admit that I have also been running the EML 300BXLS in my Art Audio Diavolo 300b SET Copper Reference amplifier as well. So I can say they have about 1000 hours on the Elrogs. Regarding sound quality, I enjoy both tubes equally and wouldn’t say one is particularly better, but the Elrog is a tad smoother, slightly more euphonic, and a tad less dynamic. EML 300bxls comes across as more dynamic and neutral sounding to my ears in comparison. I’m splitting hairs here as they both sound much more alike than different which surprises me as they are constructed differently. They are both superbly made tubes with excellent construction and looks, but the EML 300bxls are structurally built more robustly and are beefier in looks and stature whereas the Elrog feels a bit more delicate, but the Elrog probably would win a beauty content based on looks and that beautiful glow that you won’t get from the EML.
The real question is would I buy them again. Well, at their current prices ($1455), which is more than I paid a year ago, I will not be reinvesting in them because they have priced themselves out of the market imho. They simply aren’t worth the premium for that subtle of a difference. The EMLs have a much better warranty, proven reliability, and a much more affordable price point at around ~$900. More importantly, and correct me if I am wrong, but running a 300bxls at 8wpc should probably last significantly longer than a normal 300b as it’s designed to put out more wattage and they are basically loafing in my amp’s standard 350v/75ma voltage mode. If I flick a switch I installed into my amplifier it switches to the higher 450v voltage transformer windings. I then just tweak the auto-bias circuit pots from 75ma to 110ma & I get about 13wpc which is an added bonus and a very noticeable improvement in performance for certain types of large scale music that the higher wpc output setting does benefit from.