Thank you so much for pointing this out Tom. I'd noticed X-Plane seemed to maintain much better FPS in heavy areas like LA after running FSX (which is in max power mode in Nvidia Inspector) than when run first and it looks like you've hit the nail on the head. I can't wait to try this when I get back from uni.
There's a thread on the x-plane . org forum about the plane where questions/updates are occasionally answered/given by the dev team, and they stated in the last few days that they're still hoping for a 2015 release: "Target release is still 2015 and we are optimistic it will materialize. So enjoy summer and be nice to eachother"