I currently have ~2 dozen open tins at the moment and keep tins that are open and not the handful that are currently in my rotation in plastic containers(rubber gasket/airtight) that have a large boveda packet in them 62-65%. I have found this keeps them from drying out and in some cases, I have taken a rather dry tin, popped it in the container with the others for a few weeks and when I return to it, it's right as rain.
How long I can keep this up, I can't tell you for sure, probably as long as the boveda packet lasts. Also, I keep tins separated by type ie. I wont store Three Nuns or Briar Fox in the same container as NightCap or Pirate Kake for fear that a dry-er tin will absorb the moisture that came from a moist tin of another variety eg. Brair Fox with a Latakia twist. With that said, even if it is possible, I doubt I have the palate to discern this, but YMMV.