I see. That's a very difficult point, Glenn^^
The reason why I used 回 is I am talking now about college students.
In elementary, junior high and high scools, we use 年 like 高校二年生.
But for colleges, we use 回 and 大学四回生.
(Sorry, I don't know why... But as you mentioned, I felt the same way we go round and round.
Ah, this may be because college students are easy to repeat a course...^^)