So, I've been an IT professional in the past and transitioned to industrial control systems. In IT I was a contractor that only got payed for my billable hours. I spent long days but got payed very fairly for the hours I billed.
When I moved into control systems my pay was negotiated as salary, I got insurance and retirement. But when I actually started working it was all figured hourly. The problem was it didn't matter how many hours I worked, I got payed for 40. I was always told to 'take time off', but there was never time. Always another project, always another emergency. 50 hours a week and on call every night became the norm. Eventually I got sick of it and switched jobs.
Now I'm actually an exempt employee. Most weeks are 40 hours, some are more like 50 and I get an occasional call at night. My boss is rabid about me taking a day off when I get a crappy week and never quibbles when the day is slack and I leave early. My team is expected to work 40 and OT is authorized as long as the employee isn't getting burned out. The only problem with this setup is it's easy to get slack. Without the constant pressure it's easier to let things slide. I find that if I drive my team hard on a project every couple of months, they stay more productive when the workload is normal.
It's been interesting to see how the individuals react to working conditions, what motivates them (and myself), and how to make sure they don't drive themselves too hard while still getting the job done.