depend on the person's personality and body structure as i believe.......
When you ask this question and sound paranoid... (I'm just kidding.) I believe age is just a number on a piece of paper. My gran is 88 yrs old. She has never allowed her 'age' to affect how she feels. She works full-time and as a result travels into London via the train everyday, 5 days a week. She travels abroad every year, lives on her own independently, does all her housework, etc.