The freewheel is a wearing part, just like cassettes, chains, brake pads and tyres.
You have to replace or refurbish the freewheel sooner or later.
The more you ride on dirty roads and during bad weather the sooner, logically.
You can expect a lifespan of ~ 2000 km up to ~10000 km or even more, depending strongly on the conditions during use.
Some users tried succesfully to dismantle the freewheel, relubed it and assembled it again.
Personally, I think that is not worth the effort and the hassle with reassembling the bunch of tiny bearing balls.