A lot would depend on the number of rats you have, and genders. I only have two females so I only need to do it once every few days, maybe once a week. If you had a few or more boys I imagine you'd be doing it more often.
I have two boys. I change the layer they sleep on twice a week. Although they're litter trainer they still pee on their sleeping layer and it does start to smell if I leave it longer. The rest I change just once a week.
You have to be careful not to over clean. Every 2 days is likely too often. It can lead to the rats being a bit stressed as it isn't very homey always smelling clean and then they tend to overmark everythere. Which leads to worse smell.
Unless your cage is over crowded, it shouldn't need to be cleaned so often.
I do 2 cage cleanings a week. One just to switch out the bedding and one deeper clean.
I used to be able to get away with once a week. That's with one litter trained, and one semi litter trained (long story) both boys. Now that they have gotten older I seem to have to clean their cage at least twice a week. Once I introduce the other two boys I'm sure it will have to be twice a week. And that's with fleece bedding.
I have 2 girls in one cage and my other 2 girls in the critter nation cage , I cleaned one cage yesterday and just finished cleaning the other cage about an hour ago so that's it on the heavy duty cleaning , now I just spot clean every day until next week then I start all over again
I use old bath towels rather than fleece, but for my six boys I change the towels out in their Aventura at least once every 5 days. I find that the towels absorb the pee really well, and because they're all litter-trained the smell and mess is minimal, I don't have to do it anymore than that.
If I can't do it every 5 days, then once a week, or eight days tops. If I leave it any longer then things start to get kinda smelly lol