I think most painting contractors use their own speed and skills as the standard. But the fact is, most owners are faster, better, and more concientious. They do a better job than their employees.
So if you use your production rates, and expect the same results in the same time from an employee, you are setting yourself and your employee up for failure.
Set reasonable expectations for your employees. Focus on quality and value in the entire experience-- from the first phone call until the final payment. Then speed isn't nearly as important.
I know what to expect from my crews. They aren't the fastest painters in the world. But they deliver what I sell. They are pleasant to our customers. They show up on time. They do good work in a reasonable amount of time. That's a win for everyone.
I agree that 90 sf an hour is slow. I can even do that, and I'm an incredibly slow painter. But if I can give my guys 3 hours to paint a small bedroom, they don't need to bust their butt just to make the budget. They can make sure they do the job right and that the customer is happy. I've removed the temptation to cut corners, and in doing so, I don't have to baby sit.
In short, they know what I expect. I try to give them plenty of time to do it.