Torque Converter Seal, replace always during t.c swaps

My 904 trans was rebuild to hp specs 6 months ago. Car was in storage for 3 of those months. Seen maybe 1,500 miles max.

I swap torque converters while my engine is out but trans is still in the car. Seal looked fine to me so I slip the new T.C. in without changing the seal since I didn't have the tools. How fuzzy are those T.C. seals?