[Phoenix]

It all comes down to personal preference so just do whatever suits you and your hamsters. If you feel they aren't dirty and will be fine with a spot/partial clean between full cleans then I see no reason not to do so.

Personally, I clean the litter trays/toilet corners every day or second day. I partially clean any visually mucky substrate once a week and sift out any poops not in the toilet areas. I will do a larger partial change once a month, sifting out any dust that's collected at the bottom of the substrate and may also disinfect the cage itself every couple of months (always keep the substrate and nest). I just shake out the poops etc in the nest once a week (trying to keep it roughly in the same position) and discard any soiled bits then add a little extra to replace what I've removed. Since hamsters are territorial and getting rid of their scents stresses them, unless I have a reason clear out everything (illness, spilled/emptied water bottle), I prefer to let them keep as much of their substrate as possible.

If I have hamsters that share a cage, I'm even more inclined to leave as much of their scents as possible in the cage to prevent fights over "new" territory breaking out.