When does cache expires?

denisa

Using this function $this->cache->save('$cache_id', '$data', ['$cache_group'=NULL], ['$ttl'=NULL]), if I don't set the last parameter when will expire?
What value should $ttl have if I want the cache forever?
Also, when clean function is called for a specific cache, should the corresponding file be deleted? It doesn't seem to me that is deleted and I want to make sure it is fine.

admin

If you don't set it, it should last forever. By default, when a page is created in the cache, it is setup to last forever until it gets saved again and then it recreates the cache.

Regarding the clean function, it isn't attached to the Fuel_cache object (but it is to the native CI Cache object).
http://docs.getfuelcms.com/libraries/fuel_cache