I currently have my apc.gc_ttl set to 600 to help keep fragmentation down. Since apc.gc_ttl just sets the time on cache for garbage collection, I don't see any harm in keeping it this low. However, I'm new to APC, and have seen many configurations online that use a 3600 TTL, which seems quite long to me for garbage collection cache... Is 600 too low? Is 3600 too high? As I'm sure mileage varies on this setup, is there a good rule of thumb to follow?