As much as your energy fields can tolerate it, sure.
A lot of these guidelines are because these fields don’t NEED hours upon hours of playing them. A lot of times “twice” in the morning and “twice” again in the afternoon or evening is enough to get the job done.
The guidelines where it’s unwise to listen to a field “more than twice” generally has words about that. This field doesn’t have such caution.
No, this isn’t a physical change field. This is an emotional change (even if the cause of your emotion is due to physical chemicals in your body).
Just to clarify here, it’s 4 fields for “permanent physical change.” This means something like Facial Symmetry would be a “permanent physical change” but Glycolysis would not be “permanent.” (Glycolysis only works when it’s being played, and around that time.)
Have you checked out Sammy’s Official Sapienmed FAQ (Updated)? It explains the guidelines more clearly and gives you the reasoning behind the guidelines so that you can make informed decisions about your fields.