I think that passion is evolution's innovation to answer the question "should I choose to continue living?" that creatures with intelligence will no doubt start to ask. Passion keeps us happy and motivated enough to choose to continue living.
I do not think that any passion can or should be "infinite". I think that a person should explore and develop several passions. I would define passion (and love) as something in your life that is not comparable to any other parts of your life; your passion becomes the ideal.