Hmm. This gets my technical brain going all question-y.
Thoughts:
I presume that oxidation is one reason a filament fails: after all, ever cracked an incandescent? That thing burns up real quick. Oxygen is the enemy, that's why the glass is pulled into a vacuum...or filled with an inert gas. Break that protective barrier, and poof.
But...that being said...heat would strike me as being the more common mode of failure. A household bulb filament gets HOT. 120VAC running through a 100 watt bulb will pull less than an amp. But another way of saying that ..would be that it generates 341 BTUs per hour.
For reference...1 BTU = the amount of energy required to raise the temperature of a pound of water one degree Fahrenheit.
For our metric homies...I dunno what to say. Aside from that the US is in the company of Liberia and Myanmar in that it uses measurements based off of a king's *clearly* exaggerated foot size. We haven't figured out that the metric system is superior yet because we're terrible at math and stubbornly stick to awful systems because of inertia. And other things. I won't get into it, history is weird.
ANYWAYS...
So...what's a good way to visualize a BTU? Shoot, light a match. The heat energy released from that match is around one BTU.
Ever stick your hand over a lit match? Like, right over it? Woof. One star. Do not recommend.
So...that lightbulb is putting out the rough equivalent of the stored heat energy of around 341 matches over the course of one hour. That's basically a match every 10 seconds. ALL EMITTED FROM AND LOCALIZED IN THAT TINY LITTLE WIRE. Holy sh*t!
So...heat. Heat generally causes materials to expand, and a reduction in heat causes materials to contract. It also speeds the process of oxidation...that combination is deadly. And those things would last for MONTHS!
So what's the deal, Stickman? Why you talking all this talk about heat?
Well...measure the current draw of a vibe pedal. The bulb is not the only device in a vibe pedal drawing current, but it's probably a sizable chunk.
Current times voltage equals wattage, wattage times 3.41 equals BTUs per hour. You now have your pedal's heat load.
I haven't done the math, but I imagine that the difference there is quite large. Sure, it's a smaller bulb, but the filament? I wonder how the the actual surface area dimensions differ...that could be taken into account as well.
So...yeah, It makes sense to me that a small, low draw, low voltage lamp like a vibe lamp would last for quite some time, especially if it was constructed well to begin with.
My .02 c.