I actually get irritated if someone says I look young for my age. I always just say I am aging well. There is no typical look for someone of 60, 70 or older.
At 70, if you are unfortunate you can be white haired, wizened and bent with disability or still dark haired (naturally), fit and running marathons, and everything in-between. the older people get the more varied they look. Saying someone looks young for their age is based on having an entirely erroneous stereotype of what somebody of a given age looks like.