Mike Jay - great questions! Lets see here...
1) Minutes spent - it can vary, but I'd say perhaps 10-15 minutes a day is a good average. If there is enough food/seed/piles around they could keep occupied on their own for a full 2 days without much fuss, but in the extreme winter cold and if the inputs are lean we need to pile it up super high every day.
2) I don't have good metrics to say it's done. Generally it needs to leave before I'd call it aged/cured/finished compost since there is just so much coming through the pipeline. I mainly export it to our main nursery and use it as an insanely boosting deep mulch around perennials. OR, I make new permanent raised beds with heavy amounts of it and grow super heavy feeders year one (corn, squash, etc)
3) This is loose and hasn't caused problems. We NEVER would use it to direct seed or transplant in for example parsley, cilantro, salad, or other greens we may wish to eat raw. But as a deep mulch around tomatoes or to boost nursery stock, etc., its never caused us any problems.
If we had much more space I could see having bays or windrows that let it mellow on its own, but then that is just one more set of material turning, where it could be mellowing in small doses in many points in the landscape. So far we've only had positive feedback from the system, but take it as just our 2c!