How old am I?

Three elderly ladies were discussing the travails of getting old.

One said, "Sometimes I catch myself with a jar of mayonnaise in my hand in front of the refrigerator, and can't remember if I need to put it away or start making a sandwich."

The second lady chimed in, "Yes, sometimes I find myself on the landing of the stairs, and can't remember whether I was on my way up or on my way down."

The third lady responded, "Well, I'm certainly glad that I don't have that problem - knock on wood." She then rapped her knuckles on top of the table and said, "Oh, that must be the door. I'll go get it."