It's not a question of whether you want to practice or not. Landlord, except the single upper limit of 255, the total kung fu value also has an upper limit of 5 10, which means that you can practice two kungfu at most, but you can't practice six kungfu at the same time. Of course, modifiers can do it.
Also, PM doesn't have to be practiced twice. Some PM usages require three competency values. For example, a double-edged mage must give consideration to both double attack and speed, and there must be one effort that cannot completely balance the other.