Run df on your existing filesystems and calculate the ratio of inodes to disk space. If any of those partitions are used for Squid's disk cache, do you think you'll run out of space, or inodes first?
Try to intentionally make Squid run out of disk space on a cache directory. How does Squid deal with this situation?
Write a shell script to search the cache for given URIs and optionally remove them.
Examine Squid's store.log and estimate the percentage of requests that are subject to the refresh_pattern rules.
Can you think of any negative side effects of the ignore-reload, override-expire, and related options?