Hmm. Well, neither of you quite answered my question. What I was asking, simply, was: do you believe that anyone senior to you is "sempai" and anyone junior to you is "kohai"?
I don't have a good feeling helping you to hijack this thread, but OK:
Sempai is someone who "went through the door before you did". It has nothing to do with age or rank. You could only speak of experience.
One interesting point: The person who has started with you is also classified sempai.
If you search for something which includes age, you have to go back to the roots of the word sensei. But the regular meaning can be found in the wiki...