Enter the Gungeon Wiki

If you use the partially eaten cheese, and pick up and another item (thereby dropping the Cheese), you remain under the full effect of the item until the end of the level. In my runthroughs, the flight aspect of the effect lasted until I finished bullet hell, but the invulnerability only lasted two levels, and the pacman/cheese sprite only lasted until until the end of the first level where I sued the trick, beyond that point, I had no character sprite (just a floating gun).