I think it all depends on the OP’s perception after replacing the receiver. If there is a perceived difference between the old and the new, enough to cause an imbalance between the left and right hearing aid, then re-calibration may be necessary. But if not, then solider on.
Receivers are cheap and they do degrade over time. I’ve never paid separately for REM. Polish is extra.
Thanks all for your replies. As you can see, I’m a noob to HA’s and am still on a learning curve.