I made this over the Christmas holiday, which had a blinky light for the nose. A cheap bell blinky that uses a button cell battery. The actual usable life was about a day or so, but it actually did blink well into the new year before I could not detect any flash coming from it at all. I suspect the outrageous claims are based on how long they could get it to run before it actually wouldn't light any longer.
In actual practice, I presume about 50 hours of use from my tail lights that use AAA batteries. When I replace them, they still appear to be flashing nicely, but once fresh batteries are in them, I can see they are much brighter than before.