Suggestion, you've probably fairly easily got access to how long the most recently completed task took? Perhaps on the submission form include a low-resolution

Suggestion, you've probably fairly easily got access to how long the most recently completed task took? Perhaps on the submission form include a low-resolution indication of that, so people's expectations are set before they enter a podcast link? Round it off to the nearest minute/hour/day, and format it appropriately: "Processing times are currently around 3 hours" or "Processing times are currently around 17 minutes"