I bowl second shift too. I used to get tired around 8. There were times I skipped out so to rest. Bowling tired was demoralizing too. But one day after a dr. Visit and some testing, I'm no longer tired at 8pm. In fact, I'm get less hours of sleep sometimes when I'm on call and still have energy to bowl, get home by 12-1 am and wake up at 5am and do it over again.
I worked in a trauma 1 hospital and with over 400 rooms for patients. I was tired. Even when I transfered to specially and the job got easier, I was tired. Even with 7 to 8 hours of sleep, I got tired early in the day and evening.
But with crank, I was no longer tired.... Lol just kidding.... Seriously, I had sleeping problem and it got corrected. Even with less hours of sleep, I can function till I go to bed in the late nights.