My dad just retired this year and my mom has had a series of health setbacks. They are considering moving to a warmer state this summer. The closest they are considering is still 3 states away. As an only child (though stable adult), am I obligated to stay close to my parents or are there other options?
One thing you need to consider is this: If you move closer to them and become the source of whatever help they need, it is likely that they will never want to consider other options no matter how much help they turn out to need. At that point, if it becomes too much to handle, or if you decide you can't stand life in your new state of residence (or can't find a job there, or don't like the people there), it may be very difficult to change back.
I know this from personal experience because I moved to Florida when my mother started needing help (we all started in New Jersey originally) and I quickly got drawn into a position where it became impossible to leave because my mother became so dependent on me so quickly. And because I was here, my mother would never consider alternatives. "Carla is my assisted living," she would tell people. And guess what? I hate Florida. Pam is right - it's hellishly hot in the summer, from the time you wake up until long after you go to bed, and it's unpleasantly warm for me even in the winter. Florida is great for people who like to sit inside in the air conditioning, like my mother. Not for people who want to go outside and play fetch with the dog, like me. And guess what else? I haven't been outside the state of Florida since I moved here at the beginning of 2011.
I would not advise anyone to take this step unless there really is no other choice.
However, if you are bored where you are, don't have much to tie you there, and have been itching for a change, this might be an opportunity for an adventure. But giving up your job and your friends and the services you are familiar with should not be taken on lightly.
No, you are not obligated to follow along behind them. My parents never moved back to their own parent's States, otherwise my parents would be going off in separate directions, many States away, and not be together if that was the case.
If your Dad just retired, your parents are still very young. When my Dad retired, they had 25+ years of retirement on their own, and lived by themselves up into their 90's. Each had various health issues but they managed with each other.
Oh, sometimes when someone retires and goes South, within a year or two they are back up north or closer north. They might find they really miss the change of seasons where some of the southern States don't have that.