Hi Claire, I've just started to use Megazorb (fab stuff!) and I do a spot clean in the morning (get up poos and any obvious wet patches) and then I do another more thorough clean in the evening when I chuck out all the hay and replace it as well as cleaning up poos and wet bits.
So far, I've had the same Megazorb down for a week, and it's still got loads more life in it! It looks clean, it's bone dry and it doesn't smell in the slightest.
Saying that, though, I have topped it up with a couple of handfuls of fresh Megazorb once this week, when it was getting a bit thin inj places (I'd taken quite a few wet patches out that day).
I reckon that you could easily stretch it out to at least two weeks before removing the whole lot and replacing it completely.
I used to have horses, and I'm keeping the piggies' cage clean like I used to muck out the horses.......by removing pee and poo every day and then freshening the bed up regularly by adding new bedding to it.
I'm impressed with Megazorb so far, it's excellent value, easy to use and the boys seem to like it!
Hope that helps, Tracey