I was reading in the German forum yesterday that if the substrate is deep enough (and they mean D..E..E..P) then they never clean it all out. They only ever spot-clean, and if your hammie uses a toilet corner, that's all that needs cleaning.
The faeces should be left in, as hamsters re-eat them to extract maximum nutrition, and as they are dry, they never smell.
Reaaly good advice here - worth using Google Translate if you don't speak German:
Portal - www.das-hamsterforum.de