Most of the time, if my schedule can afford it, I just sharpen my skates when I feel like they need it. If I can't hold outside edges properly anymore, then it's time to have it sharpened.
If my schedule doesn't match with that of the sharpener's, and I have to predict when my skates will be dull, I use the fingernail test. If I run my fingernail perpendicular to the length of the blade (i.e., starting from the sharp edge going towards the sole of the boot) and there's no residue left, that means I have to have it sharpened soon.
Keep in mind that the edges don't wear out uniformly. In my case, the right inside edge wears out faster than the other edges.
As for stops -- if the sharpener is good, there's no need to worry. However, since you are still in Gamma, you might want to practice stops at lower speeds than normal just to get a feel of the sharpening. Also, sharper blades slow you down, in general, so don't be surprised if you find yourself having to stroke harder after a sharpening.
However, post-sharpening is the best time to practice consecutive edges.