I've had several from Chai at linear motion bearings on Ebay, never had any trouble with spindles except one which I blow up thru my own fault. This was one of the very early models which had the crappy 3 pin connector which I didn't fasten properly and it shorted. The ones he supplys now have a much better 4 pin connector with a dedicated earth and higher amp rating.
When I striped it down bearings where fine after 3years of very hard use cutting mainly Ali, some of my jobs run for 30+ hours continous and it never missed a beat.

I cut Ali 90% of the time and brass occasionaly and they handle both with ease.

Don't bother with fancy cooling radiators,fans etc all thats needed is a submersible water pump droped into darkened and sealed container with around 20ltr water.
The pump doesn't have to be massive with high flow rate so long as it's got enough pressure or whats called head height to reach above machines highest point and a bit to spare then it will be fine. Find loads on Ebay for fish tank type application just check the head height any above 2mtr will be fine,which most are.!

My machines run like this for over 3 years with only one pump replacement and that was only a few months ago.