I did that and the answer is no, it doesn't drain the battery. I DFU restored my iPhones dozens of times, each time trying with one or two tweaks for a day or two, sometimes with a matter of hours I could tell the difference and I can assure you, Zephyr doesn't drain the battery substantially.
I keep telling that in every topic I go. I have tried many combinations of tweaks and I can tell for sure about that subject.
Awesome findings! I never thought Zephyr caused drain in the past.
Chpwn also supports the heck out of it; well worth the $5. I remember seeing LOTS of updates not long after evasi0n release. Seems to have been ironed out quite well. Plus that keyboard grabber thing is PERFECT to prevent accidental slide ups.