Squats and deads are hard on your body, that's why they give results, in the case of these exercises less is more--I squat once a week--very heavy and I deadlift once a week very heavy. But it is important to pay attention to your body, if you feel that you are getting overtrained then you should squat and deadlift a bit less often, if you are recuperating very fast you may be able to add an additional squat session into your week. Everyone is different so it is difficult to give exact numbers.