String longevity is honestly subjective-truly "dead" strings cannot be tuned well/have strange "warbly" sounds/and are near impossible to intonate. But if one's tolerance for lack of initial brightness is low, of course it's OK to change them-I just do not pronounce them "dead" as fast as many do (each to their own.)
For instance, one of my Roto BS66 (they are Swing Bass) sets is going strong on a well used bass for several months, the mids are still gorgeous and the tone defined. Obviously not as bright as out of the pack, but it does not matter to me in this bass and for what I do. In theory, I should switch them out already, but they are holding on strong for my needs, so *I* deem it unnecessary.
But again, it's a personal choice, and it's ideal to play on strings that make you feel confident in whatever you are doing-if only bright will suffice, change as often as you need.