Dear Oh-So-Wise Miss Snark:
How many agent rejections (based on partials or full ms, not queries) should a person receive before they stop banging their head against the wall?
I know one could persist forever, hoping that the rejectors all just wrong -- and who knows, maybe they are -- but when would a more rational person stop?
If you're getting form letter rejections of full and partials, you need fresh eyes. Time for some beta readers with teeth.
If you're getting personal letters, and phone calls and liveried footmen delivering engraved calling cards that say "I love your writing but this particular book isn't for me" you're on the right path.