The Prince and the Prisoner

Severus Snape has invented Everlasting Polyjuice Potion, which lasts until you take the antidote. After an argument with Sirius, the two nemeses decide to switch places using the potion, from August until Christmas! During this swapping of lives, will they learn to understand each other? Or was this a VERY BAD IDEA? And where does Harry fit into it all? OOTP AU, background HP/HG.