Hmm a maximum of 10 years decent output is hardly constant. There was some right dross after that and I think Fleetwood Mac can lay better claim to constant creative flair personally. The Who are a little over rated on NSC imo, they even beat the Stones in some polls which is silly when you look...
I take it you mean the original Fleetwood Mac with Peter Green as the 2nd more successful version is 2/5ths American and most of the input came from the two Americans...