Jamieson, Fausset and Brown on Acts 15:7

7. Peter, &c.--This is the last mention of him in the Acts, and one worthy of his standing, as formally pronouncing, from the divine decision of the matter already in his own case, in favor of the views which all of Paul's labors were devoted to establishing.

a good while ago--probably about fifteen years before this.

made choice ... that the Gentiles by my mouth--(See on Ac 11:21).