When I first started breeding rats I noticed that even though they did not smell bad to me when I left them over 7 or 8 days I would see sneezing going on by the rats. I created a chart now and use it so that I know who was cleaned and when and it really helped me get into a routine of cleaning the rats every week and hamsters every 30 days. Everything to me is so much easier if there is an established system. Just the way my mind works.
Peace
Scott