According to a recent PS4 hardware review from Polygon, the DualShock 4 can be used for 7-8 hours before requiring a charge.
Here's a quote from the review:
"But our biggest complaint for a controller that some at Polygon otherwise consider the best they’ve ever used: over the course of 100-hundred plus hours with the DualShock 4, the battery life appears to sit somewhere in the 7- to 8-hour neighborhood, a fraction of the 30-hour battery life on the DualShock 3. As the system only includes one micro USB cable 1.5 – 2m in length, marathon sessions might happen on your floor near the PS4. As with the DualShock 3, the DualShock 4 battery isn’t intended to be replaced, though enterprising users may be able to find replacements online in the coming years."