Hi Bombaywalla:
That is actually my personal experience, I did own the signature mk 2 pre-amp back few years ago. It drive me crazy to change those tubes every 6 month or so. You can check with Andy at the vintage tube. After those bad experience, you think I still dare to try the mk 3 ? You may be right with the mk 3 but it will take a while for people gone though their bad experience with mk 2. I did said the sonic is good but there are so many other great pre-amp that don't have this problem. I am speaking in a reasonable mood and not in a emotional mood.