They Last How Long?

Fuel cells are one of those just-over-the-horizon technologies that never seem to get any closer. Plug Power didn't do themselves any favors by hyping their technology as something that would eventually go into every home; the costs are too great. But at least they've been able to find another market: cellphone towers. Sounds great: the cost isn't unreasonable compared to current lead-acid batteries, and including replacement costs, is actually slightly better. What I don't get -- and maybe this is something the writer of this piece failed to understand or convey properly -- is the claim that the fuel cells "last 15 hours". Huh? Are they a one-time-only operation? Or is that a function of the typical amount of fuel stored locally?