It always depends on the actual usage plus your general network coverage. For example my 1020 usually lasts 8-12 hours, completely depending on when I am doing what. When browsing the web while riding the train, where network coverage is poor, the device sucks the battery dry so fast, you can almost watch it minute by minute. Doing the same on a stable WiFi connections is much more friendly to the battery.
My secondary phone, a BlackBerry Q10 usually manages to make 14-18 hours a day on similar use. However that device has a slightly larger battery with 2100mAH, plus a smaller screen with 3.1".
The current phablet devices get nothing but praise for their battery performances, especially the 1520 set a new benchmark or two in this regard. While they have larger screens for sure, they also sport much larger batteries. The 2000mAH battery of our 1020 is simply undersized for the 4.5" display. I wish they would've dropped that camera "bump" and instead just made the overall housing thicker to fit a larger battery.
There is also not much you can do about it. There are some basic rules for manually micromanaging your battery drain by enabling and disabling certain settings depending on your needs. In addition you can always by an external charger to keep your phone charged while you're on the go. Last but not least wait for the successor and hope Nokia, or Microsoft, will include a better battery.
This is the only gripe I have with this phone, I again have to worry about the charged battery when leaving the house. The speed is decent enough for me, as is the display and general hardware. But that lousy battery is really bringing down the whole device package to a lower level. I'll be getting some external charger next month for sure.