A one-time fee for a lifetime subscription is the only form of payment I'd personally do.

I absolutely despise subscriptions. I’m sure there are others out there like me who would much prefer a single one time payment for lifetime access to the application. Leaving this here as feedback because I am absolutely 0% interested in having anything to do with the application/product if I have to worry about a subscription. Price it at whatever you’d like (as long as it’s reasonable) and even if it’s less cost efficient than 3 years of annual subscription then it’s still well worth it in terms of convenience.