So you're ultimately saying people should be given 5 hours for the car trip, even though giving them 10 would only result in a ~6-6.5 hour trip with healthy bladder relief?
No, I’m saying if you have 10 hours to do something that can be done in 5, but is optimally done in 6.5, take 6.5 hours and use the remaining 3.5 to do something useful. Maybe you’ll go on a sightseeing tour at your destination; maybe you’ll resolve a customer-reported bug you didn’t think you had time for this release.