I think that the older you are is a true testament that you embraced the lifestyle in flesh and spirit.  I mean, as youngsters, we are driven by hormones and curiosity.  Many probably give up, kids drain you, etc.  But if you are still into it +40, it means its no longer just a thrill but a religion; so to speak.  I take my wife more seriously now at 50, when she says she wants to find a new date.  I know she means it and wont back out as she would have in earlier years.