While two weeks apart is ok, and some say to do so during the initial periods of releasing years and years of bad habits, it is best to listen to your body. Flushing can be a bit hard on your system. I've found giving my body a rest for a month to be more beneficial (more "stones", better overall feeling, etc) and a whole lot less physically and mentally taxing.
You can do another flush right after the first IF you feel a "stone" may have gotten blocked and IF you're careful about replenishing fluids and nutrients, but it's NOT recommended to do repeated flushings so soon as a rule. Unless you feel you HAVE to help a blocked stone get out, it is best to give your body a rest of at LEAST two weeks. As I stated earlier, I've found at least a month between works for me.
As in all areas of health, learn to listen to your own body and your own common sense.