Because of the custom transformers this may be a moving target as far as total time is concerned.
What do you have on it now Kees ? My original estimate of 100 hours may actually be shy by quite a few hours. No matter, I'm sure your enjoying and noting the changes as the hours tick by
I have about 70 hours on it now.
I've been playing around linking it to my main system to hear how it does as a preamp. I got a nasty ground hum that I couldn't get completely rid of
I tried it with some music anyway, but it seems it is a lot better as a headphone amp than as a preamp I'm afraid. It lacks too much transparency and soundstage to perform adequately in my speaker rig. Maybe with some more burn-in, but I kind of doubt it.
I'll try again later and see how it does with the AKG K1000 / JK active 65 setup, replacing the Stealth as a preamp.