So, a recap is that the the outside temp of the spindle after 15
minutes running at 3K RPM, was 115F. (30 something degree F temp
rise).

I have looked far and wide for the answer as to whetehr this is excessive.

According to someone at cnczone, he measured temp on the bearing and
outside with a non-contact thermometer, and the bearing was 10 degrees
hotter than the outside of the spindle.

So it was, say, 130F, being a little generous, or 54 degrees C.

Barden machine tool bearing catalog says that their spindle bearings
can run at 100C. http://www.bardenbearings.com/PDF%20CD/MACHINET.PDF
My bearings are not Barden, but it is a good data point.

Another guy pointed out that Timken's roller bearing calculations
assume a temp of 130 C for the service life calculations.

So, everything points to a conclusion that 115C on the outside
represents a normal bearing operating temperature and is nothing to
worry about. Since I use this mill for hobby purposes, I will back out
a litle bit and will run it at 2700 or so RPM max.

i