[mlisowsk]

Then make it a one-time purchase valid for 3 or 5 years and after that customers need to pay again. Kind of in the middle between strict one-time only and classic SaaS that auto-renews.

Or: before SaaS we used to have the model of one-time purchase + annual maintenance fee (which was a small percentage of purchase, like 5-10%). The benefits of the "maintenance fee" to be defined by you. But it used to include updates of software and in enterprise context often support.