I do really wish they would add a lifetime tracker, in the same way that some of the airlines have. It would really encourage additional stays after the yearly target has been met. The lifetime tracker on my airline programme has that effect, even though realistically I never reach the target, it is still something to work towards.
I also think having a lifetime tier below diamond would also encourage additional stays that might otherwise have gone elsewhere. I can understand them not having lifetime gold as benefits are quite costly (i.e. breakfast or 1000 points). Lifetime silver though would have very little cost, but would still be a target to work towards at maybe 500 nights.