I like the Sketch model. There is an annual cost and during that year, I get access to the whatever versions are released. If I don’t renew, my version is “frozen,” but I can keep using it as is. Most traditional software that uses this approach will also still provide emergency updates for major security vulnerabilities, at least for a certain period of time. For a plugin or theme, I’m a firm believer that major security vulnerabilities should be patched regardless of subscription status for x major versions, just because an unpatched website can affect more than just the site owner.

I don’t like the recurring model for my own use cases, which are mostly just side projects, where I don’t need support — but I understand this is the sustainable model. What I’m less comfortable with are plugins that will stop working without a subscription, even if the “service” component of the plugin is non—existent or inconsequential (I’m thinking a backup plugin where you aren’t using the plugin provider’s storage or a contact form).