There is a way to have a sustainable business that sells lifetime deals and continues to support it.
You generally need low maintenance and support costs, but if you setup an investment to generate consistent returns for minimal dev/support costs or have a recurring stream of new customers it is possible, or charge for new features and add ons.
Do you really think that Adobe Photoshop CS purchases or video game purchases don't generate enough revenue to cover the costs and the only solution is recurring revenue?