This is such an emotive topic, and everyone doubtless will have different opinions on it.
At the end of the day, Steve owns the brand and founded the band. That said, the current lineup has been around for such a long time that I hope we don't get into the situation that only a couple of "classic" members are left and the rest are session musicians. They would still sell tickets but do they really need the money?
I would prefer them to go out when the band are pretty much stil at the top of their game. If Nicko needs a backup drummer to help him out, I have no issue with that, but I hope they stop before zimmer frames are required.