I am not sure how long it lasts, I have only switched it on for a few times (perhaps 6-7 hours in total?), last night I rode from Greenwich to Camden (London/UK) I took a fairly long route so it took around 2 hours, it was as bright at the end as it is was at the start.

(running on four little AAA 1.5v batteries)

If this stuff is anything like electroluminescent wire it is pretty good on power usage, I might be able to tell you in a few days/weeks ?