you can race as many times a day as you can get to the line.

just make sure the promoter permits multiple entries.

30 mi. races separated by 2 hrs. should be doable but might cut it tight if the finish and start are in different locations.

have your bottles for race 2 filled and ready to go ahead of time, and take 2 jerseys, pin your # on for both races prior to the 1st so that you can just change them, and not have to fool around trying to pin a # on between the starts.

good luck. race them both, i.e. dont save something for the 2nd race, you'll end up compromising both if you do. you only need to START both races for the 5-->4 upgrade.