It seems this thread has become "You know you used to be middle aged..."
It's one of those irregular declensions isn't it?
I am middle aged and could pass for young in favourable light*.
You are getting a bit long in the tooth and are you sure you're up to it?
He or she is a decrepit old has-been and hasn't got long for this world.
*Nothing brighter than 20W.
60 is the new 40 ....
I have thought long and hard about this comparing my current capacities both mental and physical with my 40 YO self and have come to a conclusion. To wit. Balls, utter balls.