I agree, I think it's easiest to see when you are enjoying sex with the same partner over time too...unless they are working on increasing their size, their size can be the "control" and you can experiment with the positions that work best for his measurements.
Better sex definitely sounds like an upside to the aging process...perhaps for some it comes down to becoming a more proactive advocate for your pleasure but very interesting to consider the physical side. Thanks for checking it out!!