Well, I never really thought about it either, that is until the week I turned 40 (that was nine years ago). I had a doctors appointment that week and also had an appointment to get my yearly eye exam. At the doctors visit, he warned me about all the usual things they do with over the age of 39, colestrol, calium (don't want to get hutch backed) and my blood sugar. Then at the eye doctors he gives me a new prescrition and it's says Bifocals. Yep, Bifocals. That was the day I realized I was middle age. LOL
But with fifty fast approaching I really don't worry much about it, as I stay fit, who wouldn't when working on a farm, and I love life, more now than as a 20 year old. I have one daughter who has been married for seven years now and no grandkids yet. So let mid-life come on! I'll dance with it.