I never run above 3600 as stated above. I have done quite a bit of cutting since then, and a couple of longer runs. With the quill extended it seems to get a lot hotter (way too hot to touch the lower bearing area). I wasn't too comfortable with that, but I don't like having to run with the quill extended anyway. The stock bearings are holding up ok though and I haven't changed them. I would not be comfortable going any faster than I am now on the stock bearings.