I have 2 Redding 3-BR powder measures. How often does one clean them to ensure consistent throws ?

I suppose I have yet to do anything except dust them off

I have a couple or RCBS Uniflows that are used regularly that haven't been cleaned in over 30 years. As long as they continue to work they won't be cleaned.

Most powder contains a graphite coating which keeps the powder measure lubricated appropriately and shouldn't be removed. The only time a measure should be "cleaned" is if it were to be exposed to enough moisture to rust its drum.

Amen to not ever cleaning one as well. If you do clean it make sure to get the static out of it with an unscented dryer sheet; They work on powder funnels as well. I have an ancient Uniflow and it has never been cleaned and it doesn't get used as much as it used to, but I still have no need to clean it.