Members who leave should retain limited app functionality for 4 months, including being able to see the account balance and contacting PP through wattbot.
There should be a new section for rejoining at a new address, at which point the app would then reset to day one scenario with the countdown etc.
The reasons are obvious, customers who go elsewhere still want to finalise, they should not be forced into the community in order to communicate, and those who want to rejoin have an easier journey.
As a benefit it would also allow PP to communicate with the customer.
Of course if they choose to delete the app that's their choice.