My strategy is to have an exponential backoff. I start a new feed set to query every 30 minutes, and if there’s no new post, I double the period. If there’s is a new post, I halve it. My reader goes through every feed every half hour, and randomizes which feeds it checks: a 1/4 chance for a 2 hour feed, a 1/48 chance for a 24 hour feed, etc.
Several people have mentioned exponential back off. What upper limit would you suggest? Someone might not post for 6 months, then resume posting daily. You might miss those posts for months.