OK so next door neighbours have given us their old rock tumbler which has no longer got its instructions. I have purchased grit and polisher from craft shop and set the first round going. It has been going for four days now. When do I stop and move on to the next stage? Every time DH goes near it he says 'My god, is that thing STILL going - HOW much longer did you say? I have looked at various websites and they differ wildly on timings - anything from a few days to four weeks - I fear four weeks is not the answer DH is looking for