I am pretty sure you do realise that is not the idea why a cooling off period is created… anyway…from the ToS, with regards to the cooling off period:
You will be charged pro rata if you have used any of the Curve services (including receiving a card).
So I don’t think you can get these Metal benefits and limits for free by making use of the cooling off period like this.
This is the Curve user community…if you post here you can expect Curve users to answer you.
If you would like Curve to answer you I would advise to ask them this on Twitter (@askcurve), since this is a general question (and not related to a specific account) they should be able to answer you directly.
I don’t consider my answer to be idly speculation. In my opinion the ToS are very clear on this (the existence of a cooling off period and how it works). The one month notice is not mentioned with regards to the 14 days cooling off period.