1 life-time, many choices, 1 at a time.

As a general rule, putting one’s title on a hanko is a bad idea. In America, titles, such as PhD or Sensei or whatever, are something people proudly tell other people (Sure, it’s a sign of accomplishment; why shouldn’t you be proud of it?). However in Japan, if you are advertising that you are a PhD or Sensei or anything, it is taken as a sign of insecurity (Since you are not a Japanese person, people in Japan would take it as a sign of cultural ignorance). Confident and accomplished people, they believe, do not need to tell others that they are confident and accomplished. Other people will judge that.