I use the cheapo from Harbor Freight. It is the one quart model I think. It runs in 3 minute cycles. I clean my BP revolvers in it. I do clean some brass in it at times. About 4 cycles and the brass is clean enough. I then rinse the brass well. The longest part of the whole thing is the brass drying. I put mine on a towell in a produce crate outside in the sun for a day or two.
My tumbler takes about 2 to 3 hours to clean brass most times. I use it to remove case lube from rifle cases most times. I also tumble loaded rounds that I used spray on case lube when sizing. (.45-70 Gov't. and .30 carbine.) Those take about an hour and half to remove the case lube.
For ready right now I use a rag, and denatured alcohol to wipe the cases clean. They are dry in less than 30 minutes. I only do this with small batches of rifle ammo.
Pistol brass that is cruddy from the ground, or range barrel get a couple of hours in the tumbler. After it is clean I load it like it is. Shiney does not shoot better.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.