It depends on your meaning... I train in formal classes at my dojang about 3-5 times a week. When my wrist heals a little (snapped it a month ago), I'll be back to formal Jujitsu class twice each week.
As for lost workouts due to being an instructor, I train with my students during classes that I teach as much as I can. Otherwise, my father or his wife will teach and I'll join the class. I know some schools have a formal etiquette that the instructor cannot train with the student. This is not my way. I will run, stretch, bend, kick, punch, and move with my students. If they can work hard, so can I. I still find time to give them attention. Indeed, teaching and training with my students is personally much more demanding than when I'm not the instructor for the class.
But, on a deeper note, the question, "How often do you train?" taken literally only deserves the answer, "All of the time". Formal classes are only a small part of your training in the martial way. The class may be the only physical part of your learning (it depends on how much time you spend working on your own), but the martial way is a living perspective that stays with you all of the time. We are constantly training ourselves to be the best we can be, to be virtuous when we can, to try to live in a right way. You may train in competitive techniques some of the time, you may train in self-defense techniques some of the time, you may only train in the martial arts some of the time, but you are always training in the martial way.