If you go to Settings> System> Battery Saver> Battery Use, you can see which applications are too demanding on your battery. Often, it is the Edge browser that is the culprit. Because the browser can run in the background, web sites full of ads or data that update in real time can munch away at your battery life. That is true even if Edge is not in use. Thus, it would make sense to expect battery life to improve if Edge could be disconnected from the network when not needed.
There happens to be a couple of solutions. One is to make sure that Edge is closed when you're done using it. You wouldn't leave your refrigerator door open after taking out a cola that you're going to drink, so why keep your browser open after you are done with it? The other thing you can do is to stop Edge from running in the background by going to Settings> System> Battery Saver> Battery Use. Click on Edge, then on Details. When you come to the selection "Allow this app to run in the background," toggle the switch to off.
Making sure that the Edge browser is not stuffing its face with juice from the battery is an important step toward getting more time between charges on your Lumia 950 XL.