I hope not to consider myself on the verge of being old, until I'm atleast 58-60. Its all in how you live your life, and the state of your health overtime. I'm currently just beyond the quarter of a century mark, and with my life experiences.. at times, I've felt much older than I should, worn down, dealt with my share of depression, and yet.. at other times, I feel as if I have the energy I had at 16 and that my true peak hasn't even been met yet. Like that old expression, "your only as old as you feel". I strive to live life as moderately healthy as I can withstand, and to not let my mind ever again sink to the dark depths that I know it can plunge to.. Optimism, staying active, and staying interested in life will keep you feeling younger than following a constant routine, especially an unhealthy one.