We'll be all over the map on this one. I'll wipe my chain with a rag if I spot sand or crud accumulating. That's quick and easy. For lubing, I guess I go by feel. Hard to explain, but as the chain dries out it feels less supple in the hand, and the sound starts to change. At some point before bone dry I'll put on more lube. I'm not super-scientific about it, and I don't sweat bullets if I'm a little bit late in getting the fresh lube on.