How often do they change the design of the field in baseball?

Answer 1

No set time or maybe never. Changes are made by a team when they are looking for additional seating or something that will generate additional revenue. Some teams actually change the design of the playing field based on the abilites of their team. No power but a lot of speed they might move the fences back to keep the other teams from hitting homeruns. some teams actually leave the infield grass longer to allow their faster runners to beat out infield hits. there are always things that a good ground crew can do to help the home team. Certain things can never be altered, the size and slope of the pitching mound, for example. Some of the major changes, such as moving the outfield fences in or out have to be approved by the league and no changes can be made during the season, only the off season unless it is a safety issue. Good question

Answer 2

Thats up to the teams, of course stadiums do change the look on the field if they host an All-Star Game, or if their team makes the playoffs, then the World Series. Some teams don't change the pattern at all.

Answer 3

For a while, the Boston Red Sox groundskeeper was changing it almost daily.