15 to 18 minutes a game tops starting for Calderon would be ideal. Just enough for him to hit like 2 or 3 meaningless buckets, while feeding Melo in the post during the beginning of the 1st and 3rd quarters of games.
Any more than that, and you run the risk of getting Curried, Westbrooked, Pauled, Kyried, Walled, or Lilliard into oblivion.
Let him run his old ass 34 year old legs until they fall off by January. By then, Grant would be closing games at point anyways, and his transition to starter would be a natural progression as a rookie.