I can imagine you could go 5 months with spot cleaning, especially if the hamster uses a litter tray. However, hoards tend to really build up in that time, and take over the bottom of the cage, and even if not pee'd on, could maybe get a bit humid and start to deteriorate - so I'd say 3 months for a partial substrate change, at which time you could "prune" the bottom 2/3 of the hoard! I say partial- you could probably still replace half the substrate (the bottom half probably, and mix it in with the new that's added).
I wouldn't spot clean every other day unless it's really necessary as it does seem to upset hamsters if it's done too often - I empty the litter tray every 2 to 3 days but let the hamster fluff up the substrate
I also wouldn't recommend rearranging the cage at all to be honest - some hamsters absolutely hate anything being moved, even an inch. They likethe familiarity of knowing what is where, andit also helps them find their way around as they scent mark everything to create a kind of route to follow. Adding the odd new thing goes down well but moving things doesn't go down well usually. I think of it as their home and territory - we need to maintain it and make sure it's safe and usable but we shouldn't mess too much with their stuff