Good idea. I received an email from myki just this morning, threatening me with unspecified consequences if I don’t validate my latest top-up by tapping on within 90 days.
Considering I live in NSW and use the myki only during visits to Mexico, the practicalities may preclude compliance.
Pausing the Myki passes will have no effect on this.
I'm sure the consequences are clearly specified: if you don't touch on within 90 days of your top up, the top up will be archived. Next time you touch on, the top up will be unarchived and will be available to be loaded on your card within 24 hours. You will need to ensure that your Myki has sufficient funds for the first 24 hours of travel (e.g. do a small top up just prior to travel from NSW).