Munchkin Adventure Time: Princess Bubblegum's special ability

Princess Bubblegum / Prince Gumball have an ability that gives +1 BONUS to items that give a bonus to combat strength. However this is listed as a One-Shot. I'm guessing that this means it can only be used one time per game? This seems like the least effective ability overall if it can only be used one time. Marceline / Marshall Lee can have a potential for +4 BONUS with a musical instrument against a monster with any red. Other characters have a constant conditional +2 BONUS. Princess Bubblegum would have to acquire quite a number of items to make her ability worth using just the one time. Although on the flip side, if this means one-shot per turn, then would the ability be over powered with a large collection of treasures?

Munchkin Adventure Time: Princess Bubblegum's special ability