Each bit of dialogue should be 3-5 minutes apart, minimum.
No way. Any more than 1 minute between loops is way too much.
Edit: For the record, back in D:OS (not enhanced) the NPCs repeat the same audio lines every 30 seconds, and often saying different audio lines every 10 seconds - and there's
still a lot of dead air in the marketplace despite it being occupied by multiple speaking NPCs.
