Im not sure where you came up with the body can utilize only 500mg at a time but ive seen data quite to the contrary and single doses as high as 5g all made it into the system.

With the above in mind I would recommend anyone to try and get a minimum of 6 grams of vit C daily, more if they can. ^ is the minimum recommended maintenance dose to hold of cardiovascular disease in someone who is healthy. When sick, the extra demands for vit C skyrocket, especially if you have a mouth full of amalgum fillings or have had an root canals, alone they can require more vit C than your bowels can handle daily.

I believe its commonly accepted to allow 30 minutes for something to pass from stomach to intestines.