We're looking at how member communications and processes have changed since the GDPR 'change'.
GDPR and PECR combined (?) should help to focus membership organisations when it comes to ex-member communications. It adds a level of urgency to messaging, as you have a window of, say, 2 years to contact ex-members after they cancel their membership. If there is no interaction over this period, you should stop communication. Looking at this practically, if a member has not re-joined (or interacted*) 2 years after leaving, it’s a good point to stop contacting them, as you’re probably wasting time and energy anyway.