Like you I've discovered that the N5 is capable of such endurance feats with battery life that I wondered whether, in my case, the 4.4.4 update had improved matters. When I did a search I found that if anything, users find that that makes things worse. But I certainly have no complaints at all about the battery life, and would go so far as to say it's good, in spite of the N5's reputation.
And yes, it's very annoying when that happens when you're trying to get a screenshot!
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