My neuro lets me take my mestinon on my own schedule, but if I take it too close together, I have some bad gastro problems. That will probably be your determining factor. My usual schedule is 60 every 3-4 hours (depending on how I'm feeling). If I go much closer than that, I have problems. However, some people can take it closer and in much higher dosages and have no problems. I think it all depends on your body.

Good luck on finding the right schedule for you!