If you keep your tax address in Portugal on your NIF record with AT (Finanças), even if that is not your own property address, then I do not imagine AT going after you and investigating how many days you stayed or not in Portugal.
It is anyway not in the interest of any tax authority in any country to deregister someone from their tax residency. In other words why would they want to lose a paying or potentially paying ‘customer’?
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