Both DH and I will be 80 in 2017, but so far have had enough smarts left in the old noggins to know there are things we shouldn't be doing anymore, so we don't. Bones get brittle at our age so no more climbing ladders to clean the chimney or washing or painting ceilings, or other things we didn't think twice about doing 10 years ago. I still wash the ceiling in the kitchen but with a long handled squidgy (I think that's the word, but if it isn't you get my drift). Inside windows with the exception of the kitchen I can clean with feet planted firmly on the floor, Our outside windows I have a pole thingy and just spray with the hose to finish off. I can still mange my little electric mantis but I'm now very conscious where I put my feet now and always look behind me before I back up.
I understand how your parents feel, it's hard letting go of things that you've always done yourself, sadly it has a lot to do not wanting to admit that you have reached that stage, I say stage instead of age when you have to rely on others as there is no fixed age when this will happen to each of us, hopefully we are all smart enough to realize when it finally catches up to you.
Annette