That's a good idea, seeding the long tail in time rather than in popularity in a sense. This would probably be the best way for me to do it, but even then it requires a different sort of investment – more storage, and more constantly online storage.

My setup is optimised for being quiet and low power, and part of that means bulk HDD storage that is mostly spun down. Seeding a large long tail of data would probably mean a lot more disk activity.