I was instructed by a training barista at a prominent SF roaster that they increase dose as coffee ages, say from 18.5gm to 20 gm over time.

If I wanted to follow that practice, what would be a rule of thumb as to when to start increasing? If I have coffee roasted on Jun 8 that was purchased around June 20, at what point would I think about increasing the dose?

Other than by taste, I am trying to isolate one of the variables and leave grind and time as being the ones to play around with.

Anyone do anything like this?

Not sure there is a rule of thumb. I follow taste and visual cues (early blonding).

Check out this classic (but confusingly titled) thread for more info: Grind, not Dose