Fortunatelly, degus don't smell if you clean their cage once a week. Sometimes they don't smell even if you clean them less often. It depends on the size of the cage, if you have very big cage you can clean it only every 3 weeks or so. It also depends on the bedding, if you use only hay, it don't absorb very well and they'll smell soon. Shavings are better, they absorb well. I was told that recycled paper shavings absorbs yet better (I don't know them because they are not sold in Czech republic).
Mice smell much more than degus and even when we had dwarf hamster we had to clean his cage more often than the cage with degus.