There has been a detail in Soarin's design that has had my interest since his first appearance without his goggles in "The Best Night Ever."
The detail is the almost constant tired-eye look with an extra line below his eyes that almost makes it look like he has bags under his eyes. This detail has been very consistent in his design both with and without his Wonderbolts flight suit and even appears when he appears to be relaxed. The only time you can't see it is when he's wearing his goggles (and in a few scenes of "Rainbow Falls").
I initially brushed it off at first because, with the Gala and his injury at Rainbow Falls I figured he was just under a lot of stress. However, the detail was there before the competition in "Equestria Games" where you'd think he would've gotten plenty of rest to de-stress beforehand. After that, something finally clicked in my head after watching "Rarity Investigates" because I had to go through the list of background ponies to make sure.
What I found was that there were a few other ponies that shared the same "tired with bags under the eyes" look. The ones from "Rarity Investigates" of course were Wind Rider and Stormy Flare, but there was also Filthy Rich and Pinkie Pie's father from very early episodes who also shared that look, and the one thing those four ponies have in common is that they are not young ponies.
Which begs the question: Just how old is Soarin' really? Because if you compare him to those other four he'd be old enough to be one of the mane six's dads.
For pictures I made sure to grab ones where Soarin' wouldn't have been under a lot of stress: