Remove cache after being unused

I need to store assetbundle downloaded with UnityWebRequest, so that I don’t have to re-download it every time I start the game. However, I want to remove assetbundle, that was not used for certain amount of days.
Therefore, I implemented Caching system. Downloading and loading from local storage works fine, but I can’t find a way to set timer for deleting assetbundle. I tried Cache.expirationDelay, which seemed as the right way to do it, but it doesn’t work as expected. If I create and add a new Cache and set its expirationDelay to e.g. 20, download assetbundle and then restart the app, this code block:

Cache existingCache = Caching.AddCache(existingCachePath); Debug.Log(existingCache.expirationDelay);

Prints default expirationDelay value - 12960000, even though the folder with assetbundle is already created.
Is there any other way that I can find out when was the Cache created, or assetbundle most recently downloaded?

I haven’t really used the Caching class. However the documentation is pretty clear that using AddCache will add a new cache to a list of caches. To get an existing cache you should use something like Caching.GetCacheByPath or Caching.GetCacheAt

If you have already created several caches you might want to use Caching.GetAllCachePaths to see all caches. Just check the Caching class documentation and scroll to the end to see all the available methods / properties.