I think 4-6 months is a bit long; I swap mine every 2-3 months because it seems to lose oomph after that. Maybe the door is easiest but I feel it spreads scent more evenly from the top shelf. It definitely cuts the general fridge funk but won’t hide an open onion or really stinky cheese, not totally sure anyone expects it to.
I think mine lasted basically all day on low (maybe 8–10h?), high killed the battery fast and was louder. Agree with the window tip — helps a lot — and ice is just a short boost, not a sustained room temp drop.