Why do I see all these posts presuming that Ronaldo will have better longevity than Messi because he's a great athlete, when historically, the more technical players have always aged better?
Off the top of my head,
Athletic cohort;
Zlatan
Ronaldo
Robben?
Technical cohort;
Our very own Giggs
Our very own Scholes
Pirlo
Our very own Carrick
The legendary Totti
The legendary Zidane
Romario
(I don't know where to place Maldini)
It's always been that way, where players that maintained a high level of athleticism into their late 30s were seen as freaks, while it was normal for technical players to play till their 40s. Messi has relied on both athleticism (crazy changes of pace, feints, abrupt stops, riding challenges) in the past.
But in these latter stages of his career he has developed his technical game in a way that should be impossible for an old player(players don't usually learn or develop technique).
In summary, no he won't drop of a cliff in terms of performances, but he won't be the same player he was in 2012 either. We'll probably all see a brand new iteration of Messi we hadn't seen before.
Cr7 is a freak though.
[Edit. I do fear for Messi in terms of his desire to continue. He seems like the kind of guy that gets homesick and he currently doesn't look like he's at home at PSG. If he never left Barca I would bet my mother on him playing till 40. But as it stands, I can only bet my girlfriend]