I have done night exposures of up to about an hour using TMax 100. I have also been thinking about working up a system for Acros 100, but have gotten distracted by other endeavors. Both TMax 100 and Acros 100 have far better reciprocity characteristics than more traditional films, so for this kind of exposure, they are faster than most 400 speed films. I think that Acros is the better of the two for reciprocity.

You might actually want film that will slow you down somewhat, for such long exposures. If there is any kind of ambient light, street lights or the like, four hour exposures are very long. You might find that something slower, or with more reciprocity failure, than Tmax or Acros would be in order.