In my experience, GS will only let you switch out a game bought with the B2G1 promo while the promo is still active (regardless of the 7 day returm policy). In reality, they should be able to do it within the 7-day period since they can just exchange one game out for another. The times that I've switched out a game from a B2G1 promo, they have done a return for all 3 games and then have rung up the new set. You'll even come out a penny ahead since they have to apply a value to the free game. :lol: So YMMV on them switching out a game after the promo is over.
Also, you picked games with different prices so you didn't maximize your savings.