Annual counts of Grateful Dead and Phish shows form a similar shape in some regards: early rapid rises, a sharp cut after 8 years or so, and relative continuity for the later 15 or so years. The Dead's curve does have twice as many sudden drops, indicating years with shorter or fewer tours. But their "hiatus" didn't even last an entire year (1975, which also included several shows), while Phish have had more years with no shows, and latter years with half what surviving Dead members peformed. Moreover, excluding their festivals, Phish tours typically hit arenas and sheds, avoiding the stadiums that became a key element of Dead tour.
(Note: An earlier post included incomplete Dead data.)