Follow-up from "Build circuits preemptively": Make things configurable.
The following discussions from !154 (merged) should be addressed:
It would be good if this were configurable. (Is it part of the specification?)
Yeah, these should probably be part of the configuration. But let's put that in after we have the configuration refactored.
This duration should probably be configurable at some point too.
Maybe this parallelism should be configurable too, down the road.