The power of three is close to light output re-rating, the actual number is
3.5. As for lifetime re-rating I did not see any restriction on the ratio of
voltages. Bear in mind that those numbers are approximate, you certainly
could not measure elapsed time by that method.

Mouser is pretty much a low life cataloger, parroting other sources and
frequently those copies are not checked for accurate re-typing. I consider a
bulb manufacturer much more trustworthy source of such information, because
it is their livelihood that is on the line, though some of them have slid
down the line of quality. For example, GE bulbs of any kind are no better
than third word products; for that matter, they are made in a third word
country, Brazil. I certainly would not trust data offered by GE's lamp
division. One reputable manufacturer is Chicago Miniature, they have been
around for long time and have good reputation for quality. There is a very
good application note in their data book; web site is: http://www.chml.com/

Regards

Miroslav Pokorni