@Lightingeye60 - If you want to get along with others don't come on this forum at post opinions as facts...

They do hold up quite well but when a failure occurs it is often the capacity but the ballasts and igniters are not resistant to fsilure. 70s-80s era GE was indeed good quality. They weren’t bad at all. They had excellent mercury vapor fixtures and great HPS fixtures. So far, the oldest GE’s hold up better than any other brand. I find more vintage GE’s than vintage Westinghouse’s. Westinghouse did make better bulbs when it came to mercury vapor, but GE’s fixtures seemed to be better at holding up. Don’t usually still see too many Silverliners nowadays. In some places I still see plenty of 1960s era M400 Mercury vapor street lights

I’m not sure about Line Materials and I don’t know too much about them. The ballasts GE used for their MV fixtures were very good. The ones from the 1960s through the 80s seem to be the best (I still see plenty of 80s M400R2 and M400A2 fixtures still holding up as MV’s as well). The older M250’s and M400’s by far are the most common vintage fixture to find in mercury vapor. GE always had very good MV ballasts. Even GE’s newest MV fixtures hold up very well. It seems that regardless of brand, mercury fixtures last longer than HPS fixtures. This even applies to Cooper and 2000s era AEL. Fixtures without igniters don’t seem to fail as much. There are even those cheap MV yardblasters still around. It seems that the ITT/Electropak yardblasters seem to last the longest. The Cooper/Regent ones weren’t too good quality and the ballasts in the MV ones failed frequently.

Of course there are people who have different experiences, some may say “yardblasters last longer than cobra heads”. NEMA heads seem to be just as reliable as cobra heads when it comes to the ballasts as I believe they use similar ballasts. NEMA heads just get vandalized more easily and the buckets sometimes crack over time. I see vintage MV NEMA’s still working all the time. The place where I live is all LED and was HPS prior. But even then, there were MV NEMA’s often used on barns or on home yards. NEMA’s weren’t used in my area to light streets usually. I’ve been to many parts of the U.S. and I’ve seen many street lights. For example, it’s very easy to find a NEMA head with a missing refractor, while it is pretty hard to find a missing refractor on a cobra head though you do occasionally see it. I’ve seen cobra heads with broken or missing refractors. Usually those are glass. Most cobra heads with missing refractors are just FCO fixtures with a clear flat lens.