I can't imagine that TNG would have had more than a single turbolift set, simply because there would almost never be a need for multiple turbolift sets.
As for two sets of doors, that seems unlikely, too, since a mechanism to keep them in lock-step (necessary, since to my recollection, it never appeared that there were two sets of out-of-synch doors) would have been complicated and required costly maintenance over the seven-year run of the show.
As for two sets of doors, that seems unlikely, too, since a mechanism to keep them in lock-step (necessary, since to my recollection, it never appeared that there were two sets of out-of-synch doors) would have been complicated and required costly maintenance over the seven-year run of the show.