My father passed away in 2009 following a short illness, he was 67 and still lived at home. The talk was never needed. My mother, now a widow, is 67 herself but functions at the level of an 87 year old. It's a delicate dance, talking with her about programs and services that can allow her to live independently. Harder yet is attempting to plan for "what comes next". Her ability to stay in her home is severely limited compared to what my father faced; she took care of him, she is now on her own.
These thoughts emerged while reading an article on this topic. One phrase jumped out at me, take it in stages. Don't go from driving to no driving at all. Gradually slow down. The article makes it sound easy, however, it does not discuss what to do if your parent is unwilling to accept your assistance or face the reality of their decline. Another topic all itself, and not an easy one for society to address.