Depends on some key factors, how many practice balls have been hit, how many rounds have been played with this set of grips. Heat, dirt, and oils from the skin also wear on the life of a grip. If your grips look worn or if they are slippery, you should replace your grips. I recommend 1-3 time per playing season.
Worn grips cause slippage, off center hits and gripping to tight with a worn grip. Benefits of new grips, fresh grips allow for proper grip pressure, which allow for proper swing mechanics and wrist action. Don’t let worn grips hurt your game.
See your local PGA Professional to find the proper Grip size, and material for you.