It is not as strange a question as it may seem and I am wondering if my times are about equal to yours.
So here is the question. How long from the moment you leave your residence to the time you return do you actually spen on one show day?
Leave out any side trips,and use only the average show and minimun classes entered. Don't forget that some times will be doubled as you need to get there AND return.
Here is an example
To barn and back (driving time) = 3/4 x 2= 1.5 hrs
Trailering and getting horse ready at the barn = 1.5 x 2 =3 hrs
At the show = 3.5 hrs with 2 classes
Total time =8 hours.