Depends on the brass and media. If it's cleaning, walnut is quite a bit faster than corncob. I use walnut with a bit of polish added and run until dry.

If I just shot and picked up nickel cartridges from the range, 10 minutes is fine.
If I just shot and picked up brass cases, maybe half hour or however long it takes me to eat lunch.
If it is range trash brass that is stained and discolored, maybe a couple of hours.

As far as finish polishing brass until it shines like a mirror (4 hours in corncob) I just don't bother anymore.

__________________
Science plus Art