Restricted Hot BA Wears for Instructors

[rips]

I work in a training Centre and would like to know if other training centres in the UK have a limit of hot wears for instructors. I have heard of examples of 1, 3, 9.
i.e. 1 a day, 3 a week, 9 a month.

If you have what evidence have you used to support and implement any procedure.

Any help or information is greatly appreciated.