I don't see anything immediately wrong with e5 but it could eventually become a weakness like our pawn on a5.
I am not sure if black would retreat with Nd7 (attacking our e5 pawn right away) or play Nd5. If he plays Nd7 we may have to move our bishop back to f4 to protect e5.
Explain how he can win an exchange, I have him losing a bishop for a pawn up after we exchange knights. I don't see a better exchange for him.