We have a lot of brightwork on our cutter, and we need to refresh it about every 3 months in the tropics. We buy these brushes by the box and are quite happy with them for varnish work.
Very poor quality. Handle snaps off with light pressure. Took 6 brushes on job and finally finished by using brush without the handle! Smaller size are better, but the foam also tends to break down quickly with use.