I'm 20 years your junior and have been wrenching on stuff since I could hold a wrench. I find that there are some things now that I'm not willing to undertake myself. It mostly comes down to time constraints - would I rather spend my limited free time rolling around under the car or doing something else? My dad is 75 and still does all his own work on his cars and house. My younger brother and I help when he asks (which is rare). This past week we've had a lot of snow and ice. I call over there to see if he needs help, but he's got it all covered (much to my mom's dismay).
I guess it comes down to whether or not you enjoy it. If you don't, have someone else do it. I still enjoy working on the older stuff like my RV and wagon, but turn the everyday stuff over to "professionals".