I tend to buy cheap shorts. I can tell within a week if they are suitable or not. If not, I can move up in price. In the end I buy 7 pairs of the shorts that are suitable for me.
One week of single usage. Then wash all the pairs at once. Nice to have enough jerseys and whatever else to allow washing once a week.
Performance Bike has stuff on sale now. Their shorts work well for me up to 100 miles at 20mph. Maybe 3 hours at racing speed.