I have one but I keep it secret
Just kidding, I didn't have time to formalize it yet and put it online.

Frequency will be customizable in a future release so you will be able to set 4 weeks.

Auto save is enabled and runs from time to time, obviously not enough in your case... sorry.

I hope so ! Thanks a lot

Thanks for your explanations, yes "operation type" = "category". I will change these terms as sou suggested.