My kids do a two-pass sharpening every week after their practices are done, so that going into games over the weekend they'll have sharp skates every time. When the school team starts up, my boy will likely do his two-pass sharpening the day of his school game and be good until the next one. This comes out to about 6 hours/sharpening for each of them. I sharpen mine about every two weeks since I only play once a week and only wear them for coaching otherwise.
We love the Sparx. We never have dull skates and the consistent level of sharpness from practice to practice and game to game is something that people don't mention often, but that is a big advantage of being able to sharpen so easily and conveniently at home. We sharpen more often that we probably need to because we can, but that consistency is a wonderful thing. My skates are always still sharp "enough" when I finally sharpen them - we've seen no obvious difference in durability of the edges between the Sparx and our local Perani's, where they do a wonderful job of sharpening.
As an added benefit, we bought the edge checker from Sparx, and using it we have found that once the sharpener is set up the edges are nearly perfectly level every single time. To be honest even the best shops don't achieve that accuracy that frequently.
My son is 15 and my daughter is 11 and neither has any trouble sharpening their own skates on it.