Use the Performance Institute on the day of a game. Save the game to a memory card, then remove the memory card. Next, simulate the game, then exit the game without saving. Insert the memory card back in and load your superstar. You will be able to use the Performance Institute again while still retaining the benefits gained from the last time you used it. Repeat this process as many times as desired to raise all Performance Institute stats. -From: Brian Hernandez

To use the Performance Institute more than once in one week (assuming if your agent lets you use it), first go to your schedule and simulate up to the day that you have your game. Then, go to the Performance Institute and do your normal drill. Go to your schedule and start your game; however, when you get to the kickoff, quit and go back to the Performance Institute. You should be able to attend once more (before the game).