I don't believe I have an ideal mate. Here's my scenario:
Say you've found your ideal mate, and you're in your early to mid-twenties. This guy/girl has everything you want in a mate, and you couldn't possibly be happier with where you are in your love life at the moment.
As we grow older, the things we like and want in life change, and thus, the ideal qualities that we search for in that perfect mate will change too. Now, looking back on the person that you're with now, you start to see that maybe they don't have some, if any, of the qualities you're looking for at this point in your life. So when things break up, you're out there looking for Mr./Mrs. Right once again.
Personally, I don't think we should look for a one Mr./Mrs. Right. I don't think we should search for love at all. True, honest, complete love comes to you, in the most random places. On a subway, in the checkout line at the supermarket, sometimes even when you run into someone coming out of the public restroom. The point is, if you want to search for someone, search for companionship and friendship and let it evolve into love if it's meant to be.