Unless there is a thermal protection that drops the power to 1/2 to prevent LEDs from frying if the fan gets stuck... Don't forget it's GE - no eBay/Alibaba cheapo lamp. But OK - we can call it "failure" because of the bad performance since that point.
CMH lamps can reach same or better efficacy than this LED lamp
The 4000K version of this lamp gives off 4,800 lm while Osram POWERBALL HCI-T Excellence 4,200 lm only. Both in 35W.
If the luminaire is very old, what is its condition ? If the luminaire is deteriorated it makes more sense to replace it to a brand new luminaire, than to hack into it any lamp that will still give poor performance because of the lumianire
The price for the new luminaire could be like 10-times more compared to this lamp. That's why.
The fan will get clogged in no time in an open luminaire, mainly by insects flying to the ligth. Might survive better in an enclosed one (it will eventually getter all the dust inside, no more dust untill the luminaire is opened again)
I don't think the power of the fan would be enough to suck the existing dust in the lantern into the lamp - it's no 1,600W hoover to move it from a distance longer than a millimeter or two. The problem is with small cracks, covers bent by sun, wind, previous relampings and so on. This is a retrofit to MV (=old) fixtures and a good half of them already have midges inside.
The current through the ballast will be lower than usual, so the losses in it quite low even if it is left in. Order of couple Watts. Actually, HID ballast efficacy is not that bad even with their original lamp - For Mercury lamp it really is the lamp and not the ballast that is the limiting factor anyway
This is to replace an 80W or 125W lamp and the 125W gets pretty hot. That's why some kinds of ballasts have been banned. I agree upon the limited current, hence a few watts only. Actually +5W would cause the original efficacy of 137 lm/W drop down to 120 lm/W only.
The non omnidirectional LED designs usually dont have all that good optics either, see some of the monstrosities out there. New HID lumianire (or even non new one, but modern design and well maintained) will outperform both retrofit and non retrofit LED lighting devices
Yeah, true LED lanterns are glaring but give off all of their light downwards and sidewards. This lamp will be half glaring, half wasting the power to the dirty reflector.