You must spend long periods of time on the bike between power outlets.

Yea, that's what three other people suggested too:
But since the TO didn't give a feedback to his thread, no one knows what he thinks.

I ordered my USB-Werk for about $55 from starbike in Germany. Try there or bike-discount.de which has flat rate ($22 when I last ordered) shipping for small orders. Subtract the 19% VAT before calculating what you'll pay in US dollars.

Regardless, you're inviting problems. The USB-Werk and other supplies have lower output when you're running a headlight at night. My Garmin will charge while riding at night if I plug it in before turning the light on, otherwise it won't. Your USB light may not work while charging. Your cable situation will be messier with a USB extension than a thin piece of 2-conductor cable.

I'd stick to a StVZO dynamo headlamp mounted below the handlebar (fork crown or leg) and dynamo taillight. Add a separate USB blinky if you want daylight visibility.

It varies drastically. Sometimes I ride for weeks with 120v power available to me nightly and others I may go for weeks without an outlet to recharge. Sometimes I will go weeks without bothering to turn one of the lights on also but they are always mounted and charged if I should need them.

Wow. I'd like to know more. Do you have a blog?