I have often had something similar happen--if I have a relatively "good" day then I'm very tempted to just do a whole bunch of stuff because I actually have the strength and energy to do it, but then I pay for it the next day about 98% of the time. My pharesis doc told me that many of his patients have told him that this happens. I will add my voice to those saying they don't know how you are standing that long! You must have some good drugs or something!

Good for you that you're able to do that, but as others have said you may want to be careful that you don't just completely wear yourself out and have your MG get worse. I wish you the best of luck and hope you can find a balance so that your off days are better for you.
MK