It doesn't necessarily have to be a "time" thing (and if it is, it does have to be smart about it).
I like the fact that Minsc got pissed off at you in the original BG if you picked him up in the party to go looking for Dynaheir, then never did that. I don't like that he would still get pissed off when the timer ran out right as I entered the Gnoll Stronghold map. The quest probably would have been better served if the timer was ignored the closer you got to the stronghold. Or perhaps if it was abstracted that if you started going in the opposite direction, then he'd get mad.
People can bitch and moan about something like this, but to me the solution seems obvious. If you would like Minsc in your party, then you're going to have to do what he is asking of you. It seems absolutely retarded that you can assure him you will look for Dynaheir, and then never do that, and have him still follow you around. If you don't want to be "burdened" with looking for Dynaheir, don't recruit Minsc.