I've only had a robo dwarf, but I wouldn't worry about it too much
If you can't smell it then don't worry! They pee such tiny amounts it probably mostly evaporates. With our robo I didn't actually spot clean as couldn't tell where he was going - so I would semi clean one half of the cage at a time and leave the other half (so he always had somewhere familiar smelling). By semi clean I mean going through the substrate and replacing some of it and mixing it in. So I'd do the left hand side of the cage - then 2 or 3 weeks later I'd do the right hand side. But really you can leave it quite a long time if it isn't actually smelly!
They will sometimes use a litter tray with sand in, if you put it inside a large house. Don't worry about poops either unless they start taking over, then spot clean a bit.