How long can a tart be kept in the freezer?

Questions like this don't always have clear single answers. Most foods will keep at least for several weeks in the freezer, and some may last months. Probably of more concern is whether or not the tart will be appetizing after a very long stay in the freezer. Experiment and see if they deteriorate in flavor over different lengths of time. I would keep that kind of thing for 4 or 6 weeks, and then come to the realization that it doesn't seem to interest anyone.