I'm doing a highly unscientific survey to try and determine if it's inevitable that bicyclists "devolve" to a more up-right riding position as we age no-matter-what or if the more aggressive riding positions are just as possible despite one's age.

What I've experienced on various bicycle forums and in real life is that many people who rode a race bike when they were young gradually buy a bicycle that has a more up-right riding position as they age... and in many cases, give-up on traditional bikes altogether and buy a recumbent or trike. The reason for this is typically, "I can't comfortably ride in that low position any more due to [insert medical conditions here, like lower back pain, neck pain, belly is too big, etc.]".