How often can I expect GC to run?

Some bugs like average disk used space this month would be fixed anyway (it’s a reporting issue on the satellites, US1 and SLC in particular, see Avg disk space used dropped with 60-70%), some - are filewalker related (but perhaps not a bugs, but errors, check your logs).
At the moment I can suggest only to use your df --si -T as a point of true. Or wait until all filewalkers will finish their job for each trusted satellite. There are 4 more, not only used-space-filewalker, did you know?