I would be concerned about the receiver/dryer having rusted from the inside out. If the desicant got saturated with moisture, the moisture would start forming acids that would attack the metal of the A/C system. The most critical being the evaporator, compressor, and condensor. I would not be worrying about the hoses as moisture and acids do not attack them as readily.
At the least, I would replace the receiver/dryer; change the compressor oil; check or replace the screen ahead of the expansion device; pull a vacuum for a long time on the warm system; check for leaks; load the requisite mass of freon; and see what develops. Maybe at the next A/C service change the receiver/dryer again.