Im thinking 16 is all OSHA allows you must be getting 2 one-hour unpaid lunches I work many 3a-7p 11a-3a 7p-11a with a two hour round trip commute, makes those 8 hour turn arounds a bear.
I've done a few 30+ hr shifts (38 straight is my record), and a few months ago did 26 straight. I usually think about the cool gun I'm gonna buy with some of that OT money. After 18 or 20, it doesn't help, but by then, nothing does.
Overtime? I wish! I ended that week with 45 hours so I got 5 hours of OT which did not even occur during that 17.5 hour shift. And I took no breaks through the entire thing! Boy was it fun...