I've read some articles suggesting a battery life of about 11.5 hrs for the Nexus 7. This is of course with continuous usage, but this isn't how I need to or actually do use mine.
Typically I shut it down at night, since I don't use it then, and even during the day I am mostly leaving it in suspend, then periodically using it -- I turn it on about 7:30 in the morning, and then shut it down at about 8-9 pm. I'm not streaming video or music, not doing a lot of emailing. I find I can easily use it for 2 days without recharging, and even at the end of the second day there is still 30% or so of the charge left. So this means a typical day runs about 30-40% of the battery down.
The external keyboard I bought is mostly unused, but this doesn't mean I wish I hadn't bought it. When I got my new "black bag", I was carrying the keyboard in it, but space was a bit cramped, and after I noted that I rarely needed it, thanks to the TouchPal soft keyboard, I took it out, so my black bag is that much lighter -- not a lot, but clearly noticeable.
I was on the verge of buying the Pro upgrade of Jota+ (simple text editor), but then I saw that the ONLY benefit is being able to load more than 2 files. I'd rather fish around for more feature-full editors, but in the meantime, 2 files at a time is adequate.