I have kept my desktop software as a one-time payment for a version N license (pay 40% to upgrade to version N+1) since I started in 2005, when this was the most common model. But I do look a bit enviously at products that charge a subscription - it would be nice to get that steady income. But I don't really want to completely change model at this point. So I may offer a choice of perpetual license or 1 year sub at the next major upgrade. It does add a bit more friction to the purchasing process though.
