Then there's the question of what they put into the set-list, along with, possibly, what they leave out. Speaking as an observer, I was moderately bemused by the presence of the number variously labelled Tombstone Eyes, Those Eyes and Good Times in the set-list on a nightly basis and the continuing absence of Mountain Jam.
And it's probably significant the first post-Dickey ABB show kicked off with a half hour Mountain Jam.
When something like that happens, you get the question of how many members of the classic line up you need to still be up there on stage using the well-known moniker. We’ve already taken a glance in that direction, but this is about where we start winding this puppy up.
Your mileage may vary, but for my money it's a case of it doesn't matter who’s there, as long as there's no one who you'd expect to be there obviously missing.
Maybe that skirts around the Dickey Betts issue, but I, for one, am disinclined to look at someone who's been asked to leave as obviously missing unless there was a substantial deterioration in what's going on up there on the stage. If that hasn't happened, fair enough.
I'd invoke the same principle if there was the prospect of, say a Jagger-less Rolling Stones, a Townshend-less Who or, say, a Bryan Ferry-less Roxy Music. Much of the reason you'd go to the concert would be to see those three do their thing, and if they aren't there. On the other hand, that outfit labelling themselves The Drifters are fine as long as they sound like they're supposed top sound.
There are any number of other aspects of keeping things going that could be explored here, but the exercise has, at this point, done what it set out to do, namely provide the basis for an article while I go about switching data around.