The answer is “how long do you expect to live”. Musicians play everyday, singers sing everyday and dancers dance everyday. Most actors sit and wait for the phone to ring. Actors need to study their craft everyday in order to be ready to work in their field.
I teach beginning, intermediate and advanced acting. Practice is the path to mastering any art form. I have students seven years old and up who study at the Actors Studio. Novice or professional the point is you should be studying if you want to work as an actor.
The answer is yes. The training for commercials prepares the actor by developing the building blocks necessary to pursue film and television work.
Charles E. Conrad was my film coach and mentor for many years in Los Angeles. We were taught that the creative source of acting was achieved by placing your total concentration of attention away from yourself. This allows the actor to work moment by moment and impulse by impulse without a predetermined outcome. In other words I do not teach a method. I think this “No Method” approach is the best for the students at The Actors Studio in Burbank.