I well know method of adjusting TC is to add some copper wire with high TC.
Have anyone done experiments, seen any information or have views on what "load life stability" these coper wires may have? the trade off is to reduce TC with 1 ppm / K, but introducing X ppm / year in drift this may not be a good idea, but would depend on application.
There have been cases where i have added 1 ohm to a 10K resistor to get it compensated. So even if the copper wire resistance would move 1% total change would be very small, but may add to the load life stability of the base resistor.
When I have done these compensators I have covered them in a thin layer of epoxy to reduce future air impact. Does that sound like a good or a bad idea? If they have some load life stability issues, and other ideas how to best treat them?