hmmm well in my limited experience I have to say I really don't (I will say yet) feel jealousy in regards to my primary. In the end we have a long established happy relationship that I can't see any reason for ending. With that security I am comfortable and confident.
However I have felt jealousy over our secondary. That was almost purely due to the fact that she would not...hmmmm...commit (in a non-monogamous way of course)...we never knew whether she was coming or going. This brought up every insecurity I ever had. When we went out, I wondered why she wasn't with me, at home she wasn't touching etc. It never officially ended or started....so I had a lot of jealousy. I hate guessing...
Will I feel jealousy with any new secondary, no idea. I would like to think I wouldn't. But really who knows.