So how much should published specs be trusted, if at all?
That depends on who's publishing the specs and what the specs say. There are examples of certain branch offices of reputable companies posting nonsensical "specs" (see discussion
here) but for the most part the major players (Philips, Osram, GE...) put out dependable specs. The other half of this question, equally as important, is knowing how to interpret the specs.
I stumbled upon this thread in seeking an answer as to whether bulb technology and durability has truly advanced that far in the last decade.
Yes, it has. See
this thread.
I still have a pair of the original Osram Silverstar +50 H1s in service. Somewhat surprisingly, it's been over 10 years, at about 35k miles.
That strongly suggests they are being underfed (starved) by your wiring. Either that, or you almost never drive at night!
Philips says that the Xtreme +100 is 200/350, 1550 lm +/- 15% (basically spec), and the Xtreme +130 "450 hours" and 1550 lm. Interestingly, the VisionPlus +60 numbers are also 250/300, but "1780 max lm."
Here's where knowing how to interpret the specs comes in. Nominal regulated spec for an H1 bulb at 13.2v is 1550 lumens +/- 15%. That means the allowable range is 1318 to 1782 lumens. Bulb makers sometimes just publish this nominal value ("1550 +/- 15%") for all their H1 bulbs, which amounts to saying "Nope, we aren't going to tell you more than it's within the legal specs". Often the reason for this is because if they published true values for all their bulbs, it would tend to make their blue bulbs look, well, as bad as they are.
Take a look at that "1730 +/- 3%". What's 1730 + 3%? It's 1782, which is the top of the allowable spec. Sometimes you can find closer-to-precise specs like this by digging long enough in a manufacturer's literature, and sometimes you just can't.
But, lumen numbers are not the whole story. If they were, there would be no such thing as an H1 +50, +60, +100, etc; the max you could go would be H1 +15. Compared to a standard bulb, filament changes are made to create the "Plus" (+30, +50, +80, +90, +100...) type bulbs: generally the filament is wound with tighter pitch on a smaller mandrel. This gives increased filament luminance and improved beam focus (because the filament more closely approximates a point source). As a result, seeing distance is longer. Light color is whiter and less brown. The "plus" numbers refer to the "up to" increase in light at a point within the beam when the bulb is used in a headlamp, not to the luminous flux of the bulb itself. In order to provide acceptable service life from a "Plus" bulb, the fill gas is upgraded and its pressure within the envelope is optimized. Halogen bulbs are actually a very technologically intricate product; there are
many design and construction parameters that can be altered to maximize lifespan, maximize output, or strike a balance somewhere in between.
My cursory impression is that the once the +50 threshold was crossed, bulb life suffered greatly
Today's reputable-brand +100 bulbs tend to last as long as yesterday's +50s.
Anyway, to cut to the chase, I'm trying to decide between the XTV and VP
XTV all the way.