I haven't heard of battery drain on iDevices running iOS 10.3.1. I'm member of an iPad forum as well, there hasn't been a problem with battery drain there either.
The latest iTunes version is 12.6. After an update, there is sometimes a temporary rise in battery usage, but that soon settles down.
That's one thread, and mostly people with problems are contributing there. You won't find people posting that their battery doesn't drain, because they don't need help for something that's working without problems. And those people are the majority, by far.
My apologies. I am probably being overly paranoid. This brand new I Phone that I just purchased, went all day yesterday with very little battery drain. Something that I am not accustomed to and I just don't want to screw things up. Loving the new phone. Russ
No need to apologize. Of course you wish to keep your device "healthy". It's new, and there shouldn't be a problem when you update.
Don't worry! We understand. The first time I ever did an update, quite a while ago (on my original iPad 2), I was nervous too.