Since funds for purchase of development rights - sometimes private, sometimes governmental - is limited, they usually try to target land most at risk for development. In our area, that means they go for land along major highways or with good access, and that is close to installed utilities. My land is not that convenient to either, so they consider me a very low threat for development I guess. I was told it would also depend on how many persons in my area wanted to sell rights. If they could get 1,000 acres or more, that would also get a higher priority.
It is a permanent move. You cannot change your mind at some point in the future and develop. In my case, since my kids say they would never sell the land, I am not that concerned. And, because I own the high ground or hills around my spread, no one else could ever build so they could look in or down on me. I would not like to be surrounded by "little boxes" and, thanks to geography, won't have to. But it is a decision to be entered into very carefully.