Also remember, if you replace the battery yourself, it's almost guaranteed that it will be rated about IP22 from then on (you can't get your finger into i, and water dripping on the back, if it's flat, won't get in). Unless, of course, you're repaired cellphones before.
Which is why I always recommend that you
don't treat opening a phone or tablet as a do it yourself project. Many people who do come back here to ask why this or that part of the phone is no longer working. Then they have to find a repair shop that's willing to repair a phone that you've opened and, since they can't tell what else you may have damaged, the usual price for "repairing" the phone is just replacing it with a refurb. And the price is something you won't want to pay,
It's normally a lot cheaper to have a place like Ubreakifix do the work. (And if the replacement battery turns out to be bad, which many 3 year old batteries do [they don't make new batteries for very long after the phone is sold], they have to replace that one for free.)
[Edit]
Samsung's skin on Android really eats that up fast.
Then use a different launcher. The "skin" is just Samsung's launcher.
Nova Launcher doesn't eat battery fast.