As I told you offline, my goal is to release new versions of my software every month or two. In addition to regular updates, there may also be more frequent bug fixes. In this scenario it's not inconceivable that someone would need their link refreshed five times in 6 to 8 months.
In practice this hasn't come up too often since I don't usually put out updates as much as I would like, and people don't ask to update every time a new build is released. When it happens I use the free link. I was unaware of the update service, I will look into it.