Orienteering competitions are about finding your way around nature as fast as you can with the help of a map and a compass. It is a beautiful sport, because even for elite runners there is hardly any money to be won, and because it is the most boring sport to watch. You need to participate to enjoy it.
I started out some years ago as old and promising. I am still both. My ambition is to win the world championship for men above 90 years of age. There is usually only one competitor in this class, so as long as you have the physical and mental capacity to move in nature, you have a fair chance.
Retaining physical and mental capacity till the age of 90 is a main reason for doing orienteering. The other reason is to have fun. Hopefully I will not win the world championship before I get old, but, then again, that risk should not stop me from trying.