My dad once complained in his 80's that he would never golf 36 holes in one day again in his life. I had to remind him he was in his 80's.
He came to live with us after he fractured his back working on his lawn mower, and lived with us for 4 years (he learned that he could not do everything by himself after his back issue).
The last year of his life I had to help him take a bath (even though that last year we got him a walk in tub / show combo), and removed the bed frame to lower the bed to make it easier on him getting in and out of bed. Pretty much tucked him into bed every night, kissing him on the forehead telling him that I loved him.
Honestly, it sucked when it got to the point we got past a walker and had to get a wheel chair for him to get around if he wanted to leave the house. It also sucked seeing how dependent he got upon us and how much he told me he thought his life sucked because he had to depend on us.
That said, I wouldn't have changed any of it for anything in the world. He lived with us, he knew that both my wife and I loved him, and we would do anything for him.
My mother in law is now 77, and we're waiting to see how things play out when she gets old. When we downsize, will have an extra bed and bath for her in the new home.
You know your life is blessed when you love your parents and they know it, and your parents love you and you know it. Yes, it sucks watching them get old, but all those times when I was kissing my dads head at night after tucking him in, I remember how many times my mom did it for me (generally growing up as a young kid, my dad wasn't always around being in the military). Then when I became a teen (after my dad retired and he was around), for some reason my dad became a butthole and I liked my mom a lot better back then LOL