Somebody gave me a box of "sign bulbs" 15 years ago and I have never had one burn out.
Sign bulbs have a sturdier filament and more filament supports (typical residental lamps support the filament only at the ends) to allow the lamp to withstand vibrations. You will find a similar construction in "rough service" or "garage door opener" lamps.
Also, operating lamps at a lower voltage will also produce a more yellow light due to the lower filament temperature.
BTW, I used to work for a company that makes programmable message boards and scoreboards, so I'm quite familiar with incandescent lamps, especially those made for signs. If you have more questions, ask, and I'll see what I can remember.
Brian
