while all this may be true, I think people who use cobs wont use them for five years. they will stay on top of the newest best gear they can. so long term testing funny to me. I don't think I ran a light system with the exception of my SE HPS's for more then two years. .
so yeah will it stay lit that long, but in 5 years there will be something much more efficient, brighter, spec's that you will want to buy anyway.
if there is original owner running 3590's in five years its will be a miracle, to withhold the temptation to upgrade.