40% of the time means 60% on the bench.
At this point, I don't see what Mes gains from this arrangement. He's already had "exposure" to the big leagues. What he needs now is playing time.
Mes is also coming off a very rocky year in 2012. Let him gain confidence at AAA. Let him work on his defense down there.
When does he come back up? We see how it goes for Mes, for the ballclub. Are there injuries? Does someone (Hanigan, Olivo, Mes) have a bad year, a great year. Lots of variables.
But to start things out, I don't see the advantage of the 60/40 arrangement. I'd send Mes to AAA, let him catch 80 percent of the games, let him hit third and get a lot of at bats. Then take it from there.