I've found an effective band-aid is 'become the supply chain'. Running your own cache, poorly, has advantages. You don't get the latest silliness by forgetting to update sometimes.
Definitely! I suggest that where possible. Some implementations require creativity, where others it's a mundane configurable option.
It's not necessarily as easy as timely snapshots. For example, not knowing when the upstream may be syncing. Signatures, release interdependence, etc.
There is intent in my framing, however. Once the cache is made... do or don't mind the cadence - the benefit is there for the moment. Performance/availability :)
This is really just a central actor to other procedures. Scanning, eviction, and so on.