Greg1 - I have several friends that own Holiday Ramblers. One is on his second one. He gave his old one to his son and the son is still driving it. HR is a long time brand with a good reputation. I would not worry about years too much. Concentrate on the specific coach you are buying. Make sure you get it carefully checked out for defects. I personally bought an extended warranty when I bought our coach 4 years ago. That way I took some of the risk out of the purchase.
It is true that with a 2010 you will likely get a diesel motor that needs urea in a separate tank. I am not fond of the smell of urea or the smell that comes out of the exhausts of urea burning diesels. I personally would not buy a motor requiring urea burning. Smell alone would keep me from it.