If Duane and Barry Oakley didn’t perish so young, they may have gone on to be the greatest of all time. They were still pretty good without them, but it wasn’t the same, and eventually the band fell apart, without Duane to keep them in line.
It’s true that they went through multiple iterations over the years, but they were still coming out with new material in the early 1990s, and doing 25-30 nights at the Beacon Theater in NYC every March for years. I think their last NYC show was in 2014.
And interestingly enough, Duane Allman’s most iconic set of work was the studio tracks be played for Derek & The Dominos for their “Layla” album.