I worked 60-100 hours weeks for a year with constantly working over 40 a year prior with numerous data above 20 hours. I ended up getting cancer, light sensitivity, and my sleep schedule was difficult to get back into sync. I was also trying to get my team to work less hours because my whole team was being burned out however I wasn't getting support from my management team at the time. I ended up with a new director, a new team as most of my prior team left, a promotion, and proper time to recover from the burnout. It took a few months but I was able to work my way back from it.

I'm now approaching a different kind of malaise as with numerous management changes our work has appeared to become unimportant to our upper management and I suspect they will be handing it over to a team openly hostile to what we do and completely unequipped for the job. As much as I need healthcare to live I'm not willing to spend what are most likely my final years in a place that I don't think cares about our customers.

All this is to say that there are most definitely different kinds of burnout. One is more physical, the other is emotional. Both impact your mental facilities and ability to get work done. Both directly work on morale, which is why the solution to burnout in employees is to discover what's crushing their morale. If people are passionate and care personally about what they do because they know they are performing important work as part of a unified vision then extra work won't result in burnout. This isn't to say that you should allow your employees to be constantly overworked, just that if occasional extra work is needed, if you've done your job appropriately as a manager the impact is severely less and the cancer if negative thinking doesn't start to creep in. Once that does it's nearly impossible to rectify unless you're very good at rebuilding empowerment.