Look man, I don't make the rules here. And yes, the rule of thumb is that you take your age, divide by 2, and add 7. Any gal under that (or even at it, some say) is too young for you. It works pretty well whether you're 20 or 60 (although I'd still question a 37 year old woman dating a 60 year old man). And it's actually more about dating - not hooking up.
That works really well for 60 year-old men. Sure you don’t know who made that rule?