I think you are misunderstanding me. I'm saying that having time in the field is the exact problem. If you have established a pipeline of graduate students and

I think you are misunderstanding me. I'm saying that having time in the field is the exact problem. If you have established a pipeline of graduate students and you have 5 of them at various stages of completion. It's difficult to convince new students to join you in a new endeavor because no one in your group does that. Keep in mind, your role as a professor is to take on students. You would also face pressures from your current students to stay in the forefront of your field as that is what they are banking on getting advised from you. If you're 20 years old, you don't care about any of that, you just switch fields.