Great question. Here’s the deal.
Currently: The Action of the Day is only open 48 hours and cannot be completed later (unless you make it your Keep-it-up Action! see below). Why? Our philosophy is to not create a long "to do -list" of undone actions for you, because this actually makes you LESS likely to do anything.
If you complete the action - great! If you don't, then not to worry - there's a new action tomorrow!
And you can always choose a free or paid action pack under "Focus" if there's something specific you're looking for!