It depends on how much data you have from each satellite.
But you should start to see a drop in a week or so (I think garbage collection is still held for 7 days even in a Graceful Exit)
Roughly my 2 x 4Tb drives (which were both full) are taking around 1Tb to 1.5Tb a week to G.E.
Started in the 2nd week of February and I’ve still got 300Gb on one drive and 1.14Tb on another left.