Calves are not my strong point and I am working on mine in the off-season as well. As far as reps and sets I think the best program includes both types of training to keep your body guessing. 2x a week isn't a bad idea though you could also incorprate more calves into your cardio activities if you aren't doing so already, jumping rope/sprints/plyos/stadiums/hills. If thee are done focusing on working your calves you shouldn't be able to comfortably walk the following couple days.