Updates less often, and keep old versions

I know you can’t speed up how often the thumbnails are generated, but how about slowing them down? Like making sure it’s not updated more than once a month? I have a site that could benefit from showing lots of thumbnails but I don’t want to overload the server by generating thousands a day.

In fact, it would be useful if there was some way to spread the load among all the times it’s used on the site. Perhaps a way to randomly choose which day it updates. i.e. if you only update once a month, and each usage randomly picks a day, then in any given month, the thumbnails should not try to update until their specified day (even if it takes longer before the server updates, it won’t ask for an update until that day of the month).

Also, it would be really cool if you could keep the older thumbnails and let the user browse through previous thumbnails by date. Maybe have a little clock icon, and if the user presses it it loads into theater mode and shows the date of the thumbnail and lets you flip through to older thumbnails. Obviously with a feature like this you wouldn’t want it updating every day, thus the above request would be important.