It is a cardinal principle to replace the receiver drier or dessicant bag whenever a system is serviced or open to the atmosphere - as per the Australian Code of Practice.
All filter driers should be replaced every 2 years or by manufacturer’s recommendation.
The Receiver Drier’s function in an automotive a/c system is to filter foreign material, remove moisture from refrigerant and to act as a reservoir to supply liquid refrigerant to the TX valve.
The maintain of the system dry is critical as the combination of refrigerant, oil and moisture combines to create an acid which actually can make the system corrode from the inside out! Moisture can also freeze at the TXV orifice resulting in loss of performance.
Generally, a receiver drier gives little or no problems but over time if they corrode and rust it can contaminate the a/c system. A common leakage spot is around the sight glass or through a cracked sight glass.
Another problem to watch for is when the desiccant material breaks down over time, resulting in major problems such as a blocked TX valves which in turn can seize a compressor.