While I agree with some of the sentiments here, I think you are wrong in respect to the finite numbers you are suggesting (three years), that measure if someone is ready for the left seat.
I don't know your background, but you could be projecting the amount of time that you personally felt comfortable transitioning. Obviously some people may catch on earlier than you and some may never at all...
To my second point- are you saying that if you can 'hack' it in the left seat after two or three years as an FO that these kinds of moves are beneficial?

Seems like you are making more of a dispositional argument here.
(Other than the warning against commuting- that is a practical tip I agree with completely)