Read/write access should be frozen, data should be saved for 1 month so you have time to react to warning emails. If you didn't upgrade in that time, it should be deleted.

Nuke the data. It’s gone forever if you didn’t back it up elsewhere. This should be a meaningful risk mitigation that I can employ to avoid having a catastrophic financial disaster.

This isn’t a limit I’m setting at some percentage above expected costs, it’s: “I don’t want to take out a HELOC if something goes wrong”