Yeah, 15-20 sharpenings if manual sharpening is done correctly! If done INCORRECTLY, traditional manual sharpening will alter the profile FAR quicker.
It is physically impossible for a human being to ALWAYS put consistent, even pressure on a skate blade when using a manual machine. On every skate sharpened, there will be spots where the operator will move a bit slower, or push a bit harder...it's just how the human body works. Add inexperience, worn down grinding wheels, poor equipment maintenance protocols, and you can see how manual sharpenings can be so wildly unpredictable. The Sparx takes the human variable out of the equation and you get consistent, predictable results. It ain't cheap...but good things rarely are.
So, yeah. If you get a Prosharp Quad profile, Sparx will maintain it through the life of the blade.