Unfortunately that's one of the problems with Android and it also produces massive phantom battery drain. I found a workaround by force stopping many of the non essential apps that maybe causing it. When my Kindle Fire HD does that and I shut off apps that are non essential, I can go from 2-3 days standby to 10-11 days on standby.
CCleaner could help as it shuts down non essential apps that are running in the background.
Another option is to set wifi to turn off when the device is asleep. Then things like gmail etc. won't sync until you wake the device. Obviously not suitable for phones but I found for a tablet like the Nexus 7 which you might not use all the time this really helps improve standby time.
To the OP. I've had a nexus 7 2013 for almost a year now. It is a great tablet (but not as good as the iPad Air). If you want/need a small tablet though it is the way to go. Better than the non-retina iPad mini which is the other small tablet I have experience with. The screen is probably the best on any mobile device I've owned (including the iPad Air...). Performance is pretty good for a budget android tablet. On a small android tablet, phone apps will work just as well as tablet optimized apps so the app disparity between iOS and Android is much less severe. Unlike my 2012 nexus 7 which by the 1 year mark was unbearable the 2013 version is holding up very well. Feels basically as fast as it did when I bought it (only issue is I've bought faster devices since: aka Nexus 5 and iPad Air).