40 hours a week? I've done it in the past it's not realistic. If you schedule one interview per day, you'll burn out quickly. You need breaks in between to digest the previous interview.
Then again, maybe you meant that too... :)
If you do need a break between interviews, submitting new applications or working on your skills makes for a decent filler. Like a regular paying job, you'll get out of your application efforts what you put into them.