I can assure anyone who's interested that being fit, able to walk without pain, breathe without wheezing,, and able to live independently is absolutely worth aiming for. Start thinking about and doing the correct eating and moving years before.
Don't think that, just because your heart may not want to let you walk briskly, you should stay at home. Get out there and start slowly, taking a few moments rest here and there, and you'll find that you'll become able after a while to keep going for further than you thought.
Fortunately, I have quite a few friends locally, and others who live too far away to see more than very occasionally, but I do not want to be the last to go. In view of my heart - the new valve is now six and a half years old - I don't think this will happen, but I'll certainly try to make the most of my time until then.