Acording to Skates.com ice skates need sharpening around every 20-30 hours of ice time (depending on the ice and the skater this can vary between extremes of 10 and 40). This sounds about right, though usually mine get done when I realise I don't have enough grip any more. Hence this idea.
Things it needs to track:
- when you last sharpened your skates
- how many hours ice time you average between sharpening
Depending on how nerdy the user wants to get, what kind of ice they're skating on, or even what they're doing when skating as this might have an impact.