I would agree with leathermang about the r/d change except that, out of curosity, I have cut open every filter drier I have ever replaced. The ones from 123 a/c's, at least all of the ones that I have replaced, don't have a dessicant bag, they have a one piece porous "rock." Every one of these rocks have been intact.

If you WERE to decide to replace the r/d as a preventive maintenance measure, I would suggest that you drill a hole in the bottom and see how much if any oil drains out, then add that much to the system before evacuation and recharge. Breaking every connection and replacing o-rings probably introduces much more of a chance of introducing a leak than it does for preventing one.

Best of luck,