I can only speak from my experience, even though I'm only 26.
I had 3 short relationships that only lasted for a few months, each. My first ex was when I was 23. (Yeah, I started dating late.) I feel that I dated because I felt a void and that it would be nice to have someone to spend alot of time with.
My 2nd and 3rd ex were from interests that I enjoy. The 2nd one was someone I thought I would spend the rest of my life with but it turned out that he was taken. The 3rd had to go back to his home country and I have no intention of moving to the otherside of the world within such a short time in our relationship.
I am currently dating. So this is my 4th relationship. This is with someone who had been watching from the sidelines while I was dating the 2nd and the 3rd.
I seem to be dating alot in such a short time for an INFJ, eh? Maybe I'm lucky and with this current relationship, I wasn't in the mode of searching for anyone. I thought I'll be contented just by being single.
I don't know if I helped but maybe from what you have read could give you some insight.