FYI, controllers also need a medical for their job... so if you get into some kind of accident or develop a disease which would cause you to lose your pilot medical, you would likely not be able to pass the medical for the ATC job as well. Although, I did hear that if you've been working as a controller for at least 6 years and then you lose your medical, they will give you a desk job instead of just firing you.
And I do agree that a dual pilot/controller career would be really difficult, if not impossible... I'd think too many scheduling and rest issues. I'm sure there are controllers who fly for leisure leisure though. I've even heard of a few controllers who fly for the Guard or Reserve. Who knows, maybe if you try hard enough, you can make it work.
As far as that 2-year period deal goes, that's what I heard too, when I was in the program... though, I also heard that they were trying to change that rule, so that applicants can delay their decision every year until age 30 instead of having only one chance to take the job offer. I don't know what the status is on that proposed change though.