The MSCOM Team did a great post on their blog a while back about recycling of IIS AppPools and how to verify and monitor the recycles. The post included some nice samples scripts for LogParser, to ease the monitoring.
It’s great for availability and reliability but it can also be masking real problems with code running in your applications. If you are recycling too quickly based on memory limits you may have a memory leak that should be looked at, if you are recycling due to ping fails or other errors, you may have a more serious issue to look at.
Read the full post: Yes, We Recycle!…That Includes AppPools.