.. a couple things to note:
1. By non-recurring, I mean you pay for a specific period e.g. 2 months, but your subscription is not automatically renewed at the end of that billing period.
2. By "pay once" I mean you access the service as-is but forfeit access any future updates and upgrades.
For recurring / non-recurring depends on the product. But the model of pay non-recurring is something I prefer in a private setting and sometimes even in a business setting.
If use you product every 3-4 Months, let me pay for the month I use it.