Interesting point about the duty cycle. Point taken about the water cooling, good to know. Are all the 9kw spindles they put on Chinese units water cooled?

Yeah I frequently run it for more than 4hrs. Not always continuously thought. I recon the issue started not long after I set that machine up milling a marathon 10hr finishing pass on a 2000x600x100mm epoxy tooling board! I'm going to keep going with the air cooling as I do a lot of foam carving and the spindles dont get hot doing those. I'll get a news set of bearings!