How long should Pre amp (12au7) tubes last in Rogue Preamp?

I've always heard Rogue equipment drives tubes hard. My RP-5 (purchased in OCT 2017) still sounds great with the stock JJ's. No distortion or any added noise. Typical life (in hours) of general 12au7's for a Rogue preamp? I may try the newer Gold Lions next time, although I am happy with the sound of the JJ's