No problem, WMS, I don't know everything and your input is certainly valuable.
I wanted to interject here that I recently converted on of my mills (Shizouka) from steel ball to ceramic Hybrid bearings. This is a retrofitted manual machine, so it was not designed for sustained moderate high speeds, meaning there is no spindle cooling. It is a simple grease packed bearing
I was getting near 200 degrees F
when running steady at 5000 rpm for 5 to 12 hours. This was nasty and really made a cold tool stick hard in the spindle, enough so the toolchanger couldn't get it out. The spindle actually got the the point of jamming and scoring the spindle housing, it was so hot upon retraction. I had to insert cool down periods before I could do a tool change
Anyways, after the ceramic hybrid was put in, the same spindle runs at about 115 degrees F, no matter how long I run it. They were pricey, but I feel so much better knowing that the thing is not destroying itself when running at high speeds.