In reading forums since 2005...it seems the 600 watt digital ballasts and bulbs are the MOST troublesome. 400 and 1000 watt systems not so bad. Plus the 600 watt bulb selection is very small, compare to other sizes....that's because industrial users ..prefer 400 and 1000 watts.

There are a LOT of 'Made in China' digital ballasts/bulbs on the market/internet...that ain't worth a damn...beware.

Magnetic ballasts are UL rated...very reliable...with an average life span of ten years for ballasts made in USA/Canada.

Magnetic ballasts-60Hrz
Digital ballasts-240Hrz...they drive the bulbs harder.