Grobets are lifetime tools. If you treat them well, keep them clean, and not all thrown in a drawer with other files. Uniform tooth height is very important on your final finishing, and in this the Grobets excel.
I think the finest I've ever used is a 4/0 swiss pattern, and that is pretty fine. my favorite all around is a 2/0, plenty rough for fast stock removal, but gives a pretty good finish, as in ready to switch to stones. Having a set of 4/0 would definitely save me time, but I'm too cheap to buy them.