What reasons are the surgeons giving for doing both knees at once? Can they refer you to patients of theirs that went through it and were happy? It sounds like you are in good health otherwise, so anesthesia should not be a problem. I was lucky in not needing my 2nd knee done for over a year from my first, but I agree with others that rehab will be so much harder if you don't have one leg available for stability, and you'll be dealing with double the surgical pain for both legs.