I have also found that significant improvements appear with a time lag after you stop practicing. It's how our brains re-wire themselves in response to practice. The learning doesn't happen instantly, it takes some time to sink in, if you will. Think of it as a surprise gift you get to open each time you sit down to play.
As for the open F chord, I find it it much easier to use the barre F instead. I've been playing for 5-1/2 years now, and still haven't bothered to learn open F :0)