Actually, the Android version of Memento has a trigger "at scheduled time". If you wanted it hourly, you could always have 24 of those triggers. Or perhaps you could have an external app open up a Memento library every hour, and have the Open Library trigger perform the export.
If I was doing this, I would not burden my main library with all of those triggers and export Javascript code. I would create a separate library to contain the triggers and code, and just have that separate library scan/read the main library and then write the desired records.