Our W3TC page cache takes 1GB for a site that has a low amount of traffic. Garbage collection is set at 300 seconds, but still the folder wp-content/cache/page/000000 is filled with subfolders from various days and months.
We suspect there's an issue preventing the garbage collection running properly. We are using Disk cache: Basic without any cache priming.
Emptying all caches manually solves the issue temporarily, but needs to be done frequently to avoid the cache growing to monstrous proportions.