Everything I've read has said to not let your N7's battery drain dead or even close to it. Letting the battery drain down to 5% or less may degrade the quality and life of the battery. I always recharge at no lower than 15%.
I'm not a heavy user (no games, some streaming movies, no music other than Spotify). I use it mostly for web surfing, reading, and a few other basic things. I usually can go 3 days until I hit around 25-30 percent, then I recharge it. With how I use my N7, I'm sure I could go 4 or 5 days before I hit 10%. I usually recharge it every night unless the battery level is higher than 75% -- not worth it then.
By the way, I usually spend between 3-4 hours per day using my N7. I also power-off at night -- most of the time -- and it usually stays off during the day until I turn it on in the evenings to use it. Brightness is set to Auto. Wifi goes off when the device goes into sleep mode (two minutes of non-use) and I close unused opened apps as I go. Also, I don't use an app killer (heard they're not really doing you any good), nor do I have a bunch of 3rd party funky OS intensive apps running in the background other than a battery indicator -- I only have the apps I want on there. If there are apps I haven't used in awhile or don't think I will use much in the future, I delete it off the device. I can always re-install them back on the device later through Google Play. Animation is set to off and many of the apps that I don't care about if they're up-dated on a regular basis, I have them set to not up-date.