It depends.
Some colleges have more than one DoS for a course, so you may be assigned to a different DoS each year, depending upon your chosen paper or DoS's availability/schedule, etc.
Also, DoS may move to other college/university, have a sabbatical or assigned to other job that unable him/her to take up the task of looking after the students.
But
in general, you have formal meetings with your DoS only at the beginning and the end of a term (unless you have some special problem), as his role is to make sure you're
generally on a right track on your academic progress, so actual 'formal' contact time with your DoS is not that much, anyway. On the other hand, you see your supervisor at least once a week and supervision is the most intensive and important time you directly have with an academic staff, so they will play more crucial and direct role in your academic life.
But some DoS are more keen to get involved with their students, beyond their expected minimum role and be more supportive than others. And some just want to get away with doing the absolute minimum and go back to their other work/own research.