i have been running my 7 1/4 for TWO YEARS behind my V8 and this is the same original 7 1/4 that was in the 80,000 mile car. it is STILL working like a charm
Keeping oil in them has a lot to do with how they last. I have never replaced one because it was bad but I don't run a power house engine either. I have seen some Dana 60s trashed too but generaly it was because they ran them out of oil. Drache isn't running big horse power.