I'm 58 years old and I had both knees replaced just over a year ago... couldn't be happier with it. I did knee excercises for 2 months before the surgery so the muscles all knew what to do when the day came. I had a spinal so I was awake for the 5 hours or so that the surgery took. Very interesting. While waiting in the recovery room I could do leg lifts and could completely rotate both feet. Had the surgery on a Monday and came home on Friday... we live in a raised bungelow and I walked up the 2 flights of stairs. I went to physio 2x per week for 3 months and haven't looked back since. Still exercise the knees every day to keep the muscles strong. I highly recommend having them both done at the same time... I doubt that the pain is any different. Both my knees were shot anyway so one knee would have been no help whatsoever in getting through a single surgery. My knees are the ceramic ones because I have a metal allergy and couldn't have had the regular ones.