If they are trying to find something, what keeps them from always picking the new place? If they stumble on somewhere they've already been, what keeps them from just leaving immediately and rolling again (and again, and again)? I think I'd bake the exploration into the move so that neither of you get to decide. (e.g. 10+ new place, 7-9 old place).
What's the fun in finding an old place? Is there a puzzle where you have to return to places? Are there wandering monsters or other teams? Is there an overall time constraint? Maybe the maze is slowly filling with water. Maybe you have a countdown until another team finds it and another countdown until they get it back out (first find the sword, if the countdown ends, you find the sword room with the sword gone on your next roll and then its a race to find the other group and steal it back).
Good points all around. To add perspective and at the risk of being that guy who asks for help and then moves the goalposts around: Three factions (call 'em "teams") aside from the PCs are also trying to get their mitts on a magical sword which is held by a man sentenced to this endless prison maze a decade ago. They're wandering around as much as the PCs are and also know what the PCs know (the location of the exit and the location of where they came in), but nothing more. In addition to the teams and PCs wandering, the man with the sword also wanders. So do a few of the monsters (e.g. The Minotaur, a part-bull, part-golem creation whose job is to keep everyone but the man with the sword OUT of the mazes and the dabus who keep the place clean). Some of the other monsters will just stick to certain areas unless the fiction dictates otherwise in play. Nevertheless, with multiple people converging on the same goal, time is of the essence.
Accidentally backtracking to a previous location is boring, which is why I wrote in that "something has changed." That could mean any of those wandering threats are in there or something the PCs did in a given location is undone or there is a clue pointing to someplace or someone else (just spitballing here). As the move is currently written, it's also helpful to go back to a place you've been if you're taking the -2 ongoing as you can regain your bearings and lose the penalty. In any event, going back to a place you've already been, while sometimes helpful, will take time. As noted, time matters.
Given this, how does the move look now? I like the idea of baking things into the move so that I don't have to choose myself but I'm not sure how to do that. Please poke as many holes as you can in it - better now than during actual play! Thanks for your help, much obliged.