If you set a time for your meditation and are able to get up earlier, should you still keep your original time?
Yes. If your time to meditate is five-thirty in the morning, at that hour your soul will knock at your door, so you should be prepared. Choose the time that you feel is best, and stick to it. If you want, you can get up half an hour earlier in order to shower and get ready, but then you should start to meditate at your appointed time.