Behavioral scientists have discovered that one of the most effective ways to create an enjoyable experience is to stack the painful parts of the experience early in the process. Psychologically, we prefer experiences that improve over time. That means it's better for the annoying parts of a purchase to happen early in the experience. Furthermore, we don’t enjoy it when painful experiences are drawn out or repeated.
For example:
If you’re at the doctor’s office it’s better to combine the pain of waiting into one segment. The wait will feel shorter to your brain if you spend 20 minutes in the waiting room rather than spending 10 minutes in the waiting room and 10 minutes in the exam room.