My phone took about 10 1/4 hours to drain completely flat where the phone shut itself off.
Just an FYI, was talking with a tech at a Sprint store today about the EVO 3D, comparing it with NS4G. He said biggest differences were battery life as bad or worse than the HTC Thunderbolt, more bloatware than original EVO had on it, only about 1 gig out of 4 gig internal memory left for users to store apps on, comes with Android 2.3.3, will not get 2.3.4 till sometime 2012, still has Qik for video conferencing, Blockbuster, and lots of other crap. I never planned on getting it, but since we are talking about battery life, thought I would mention it here. Also, it has same signal problems as NS4G, but worse, antenna is poorer quality than NS4G - NS4G signal problems due to software bug, same as volume issue. Both due to be fixed with OTA update sometime soon (hinted at couple weeks or so). Tech not sure if HTC will fix the antenna issue before release.