The 30 - 40 gallons of sap will cook down to less then a gal of syrup. If you get down to that you won't have enough to cover the bottom of your pan. and will turn to burnt sugar in a second. Flow is very important a head tank and valve so you can let a little in to keep the pan in sap. The goal is sap on one side syrup on the other in between in the middle. More sap = more taps= more syrup = more time = more wood see a trend here MORE! MORE!! MORE!!!