I likes my half hour lunch. Seems to me that the lunch break should be at the middle of your work day. If you normally work from 7am-5pm, then noonish would be a good lunch time. And really, If people aren't getting paid for that lunch time, then it don't matter much of it's 20minutes or 40 minutes, does it?
I used to work for a place and we talked the boss in to giving us 40 minute lunches. We would eat for the half hour, then start getting going after that. The first ten minutes after lunch were always slow---people putting their PPE back on, saddling up, starting the equipment again. That ten minutes gave us a bit of time where we new we could take our time letting the food settle and not feel like we were wasting the company money. Whenever I footlock right after lunch, I have a hard time keeping the tofu down!
love
nick