One year of strong service so far.
I've been driving this Preferred Series 5AR4 in an Allen Accomplice (Deluxe Reverb) for almost 12 months so far, and it's held up great. Voltages haven't drifted by more than 0.8 volts in that time, which is a very good sign. It still looks new even after around 500 hours of use. I'm very confident in this tube. Well done, Tube Store!