Is your 3D holding charge as it always has? That could be the battery, hard to say. Mine doesn't act that way.
When a phone hits 100%, the charging circuit shuts down and doesn't kick back in until it hits roughly 96% (92% for HTC in 2010, about 96% since 2011.)
They don't trickle change (constant low level charge at 100%) as a required safety feature. If they did, your battery would literally ignite.
When your 3D is truly at 100% when you plug it in then by the time you've finished watching, it'll have spent less time letting charging power in than the same session beginning at 90%. Hence my question about which battery and its age.
Sorry about the energy saver thing, I was following best I could.