Just fyi - I do a fair amount of mass metrology at my work and deal with precision comparators that measure down to 100 micrograms values. those scales are always left on and stored with the scale's full scale mass on them. I always leave the highest value check weight on mine between loading sessions. It really seems to help with zero repeatability.
That is very useful info- it seems contrary to what my seat of the pants 'common sense/mechanical history' has been telling me for years.
My biggest question is, are the styles of construction/design of the precision comparators the same as our relatively cheap dillons, rcbs's, etc? And therefore, will storing ours in a like manner also be beneficial?