I dunno, but while it's hard to absolutely isolate aero advantage, I set all my PRs on my Argent wheelset, which I swap between Ksyrium Equipes on one bike, while I have another bike with either Velocity Aeroheat or Mavic Open Pros rims. Regardless of the mix-n-match, PRs all belong to Argents.

I'm firmly of the opinion that aero helps carry speed and allow a higher average during recovery or sub-max efforts, which then allow longer, harder max efforts. If I can drop back to Tempo and shave another 5-10bpm, I'll last longer and have more punch for efforts. Aero wheels are like Viagra, you see?

It's almost impossible to look at a typical ride and quantify what you did with the extra energy; I might average 19.2mph over 50mi @ 1.7k ft elevation one day, but grab a segment PR another day over the same ride while averaging 18mph. Does the lower average mean the aero didn't help? Of course not. Could've been weather, traffic, or just the goals of the ride.

Like Silvercivic27 said, the beauty of aero wheels is that they're at your service anytime you want to take advantage of them. I don't need to ride as hard as possible all the time on every single ride to derive benefit, so while I might make several seconds on a 40km TT, I'm happy to take two seconds on my favorite 1.5 mile segment when I drop the hammer and go for it. Netting than one PR is all the result I need to know the package is working.