This is an issue that is well-known to any advertiser who has uploaded several thousand terms, and yet seems to be a mystery to Yahoo's 'support' people.
In the past, I've sent them dozens of megabytes of our log files showing slurp hammering our servers as it checks our submission. If you use the bulk upload to modify your listings, slurp will check both the old and the new versions ... sometime at rates up to 20 hits per second or more and often continuing for many, many hours (over 32, in one case).
Y 'support' has no idea what is going on. We end up blocking the bad (terribly rude) spider for a few days and it finally stops coming. Seems to have no impact on whether the listings are approved or not.
Actually, we have noticed this effect most definitely having an effect on the status of the listings, as we will end up with hundreds or thousands of declined listings with the reason being "broken site". Ironically, only appearing broken because YSM's own spiders brought the site to it's knees!