I see the standard options for RSS feeds and how to enter additional feeds, but I'm talking how many threads per feed are imported. Had these active and ~40 threads were imported. Where is this number changed to say 1 thread per 12 hours?
Snog to the rescue again. The "Post Limit" option in his RSS Feed Filter add-on will take care of what you're looking for, just leave the 'fetch' setting to 12 hours and make the post limit to be 1, that'll limit new threads from that feed to be no more than 1 every 12 hours.
As an alternative, you can use the same add-on to put all new incoming entries for the feed to be in the same thread so each new entry will be be a post response in a single thread.