I don't think you can 'Work" brass by tumbling as your not actually squeezing or expanding the metal.
Even it does get a little worked by bumping into other cases the last step prior to priming and loading is a hot lap on the Vertex Annealer (pun intended) When you cough up almost $1700 for a set of forming dies you don't want to cause premature wear with dirty carbon encrusted brass.
Tumbling time would also be dictated by the type of media used, I use the over the counter Lyman treated corn cob which seems to do a good job.
My smaller cases generally get 30-60 mins but the ex-army used 50BMG brass takes much longer to achieve the same lustre.