Would like an "Auto-Empty" feature Rated 5 out of 5 stars
Will brief summarize suggested feature and why. Based on testing in a porting lab:
Automatic empty of ENTIRE cache at a predefined cache threshold. You already have reload on success, so it can integrate nicely. Nobody has this feature AFAIK, so you would have something unique. User choice or developer preset. 75mb, 100mb. Better would be 50% of total, 90% of total, etc.
1) In the old days disks had slower I/O but the head had smaller platters to manage. Today faster I/O, but larger platters. Its a wash. Firefox considers the default size of the cache based on free space (they may change that, but see #2). Past 100mb, disk thrashing begins. By 200mb, thrashing is bad. On larger platters, not good.
2) FF spends more time pruning cache to make room when cache hits max capacity (a read, a write/delete, then another write with new cache entry). How does the pruning work? Look at google/youtube entries in about:cache. Why I capitalized ENTIRE cache. If its expiration some of the cache may never get removed.
Example(s) Auto clean at 90% of max, there would never be a hit for pruning. Auto clean at 50% of max, less disk thrashing, no pruning hit.
You have some good points in there.
Auto-cleaning has been suggested before so I plan to look into it. No promises that it will ever become a feature.