I'm worried about a completely automatic cache, because there's no easy criteria for complete pre-caching or deletion, and the system cannot make the correct decision by relying on a crude timestamp, or the latest games I played. Imagine if I just purchased Gran Turismo 7, I will want to let it cache 100% and never delete it, I want it all there immediately, always, even if I haven't played for a week waiting for the next online challenge to go live. OTOH, if it's an adventure game, I'd prefer to delete it right after I finished it or platinumed it (platinum is now a verb). Sometimes I browse and play a dozen games, just finishing some trophies, that would flush ALL my favorites from the cache. I have a higher chance to play a game I haven't played for a while than a game I just finished.
I think the best way to handle this should be to do provide a method for manual delete, and to provide a caching choice per game: persistent cache, session only cache, or automatic cache. (default being obviously automatic)