In general with everything in China always the earlier the better, because there is always a certain amount of unpredictability with any kind of visa rules and processes. For peace of mind, we recommend to apply for your visa about two months before your planned arrival date. In very last minute situations, we have had students secure visas within just a few days before departure, however as this can be quite stressful (for you and for us) we recommend to avoid situations like this whenever possible.