Free Usage vs On-Demand behavior

Once a seat starts consuming On-Demand usage, is it still possible for subsequent requests to be counted again as Free Usage?

More specifically:

  • Is the transition to On-Demand permanent for the remainder of the billing cycle, or

  • Is usage evaluated per request, allowing requests (e.g. Auto / Slow, low-cost models, low load) to still be routed to Free Usage even after On-Demand usage has already occurred?