Ok so In general I hear that if the bearings are not made for axial load, obviously keep the fan horizontal. But in the case of having to use the fan vertically, there is no consensus as to whether to go up or down shaft because the fans can be designed specifically for both, up, down or just for axial load. The mystery fan does have ball bearings with spring loaded thrust bearing (cheap, but still a thrust bearing) and the manufacturer does not see a problem with the orientation. Someone suggested that dust would be minimal because of cooling ventilation, however these motors are hermetically sealed and all brush dust stays inside. It does not look nice when you open an old one, that's for sure. I think I got my question answered, basically if the bearings can take it, it is OK, but for sure vertically mounted motors will have reduced life over horizontally mounted.