I would expect cast members to stay put in venues that aren't changing. Jon, Lea, et all could have a home and friends nearby so staying for a year or more is not surprising or unusual.
Road shows are another matter altogether. With a few exceptions, they are changing cities weekly, living out of suitcases. As a business traveler, I can barely handle doing that one week a month.
I just saw the show for the first time a couple of weeks ago also. My guy and I were both so overwhelmed, I bought the CD the moment I got back. The cast was superb, and I was especially amazed by the little girl playing Wendla, who I think both looked and sounded closer to the role than the original did. Just my opinion.