I'm confused.

If you rarely buy return tickets you are paying a significant premium for your one-ways. Is this in economy or business class?

You don't say what it is you do that necessitates this kind of travel, and whether it is self-imposed or a requirement of your profession (and it is your good right not to) but I suspect you are an ideal candidate for a real live human travel agent that can probably streamline your travel patterns and save you a lot of money. As far as the FFP go, you'll need to post much more detail regarding airlines and locations before we can start giving you really useful advice.

Welcome to FT!