I got my Helene DAC last December. I leave it on. I found it takes almost a day to get optimum sound. I burned out the original rectifier tube in June. Calculated 7000 hours on the tube by then. I had shut everything down for 9 days while out of town. When I got back the DAC had no sound. The clue was the LED in the back right corner was dark. The rectifier tube still glowed even. My dealer sent me a Sovtek for replacement. A few weeks later I bought a Mullard reissue for backup. Decided to try it just to make sure it worked. Sounds better than the Sovtek so I left it in.
My question: Do you leave your DAC on? Love to try a NOS Mullard but reticent to spend that much for a tube that will last me just 7-8 months. Did you make the decision to just stick to the NOS Mullards full time?
I stocked up on some E810F, E180F and some 6J11P tubes. In every case I ordered tested, matched pairs. I asked my dealer for some extra E280F tubes but have not heard back from him. For now I have an estimated 30 year supply of tubes for my DAC. Not expensive but not just available anywhere.
My take on the Helene: Excellent music maker with PRAT that rivals my analog. I had to upgrade my streamer to get the same level of music like my CD Transport. Ended up with the K50. Can't get enough of the music. I've played about 10 hours of vinyl since January.