I’m going to make an embarrassing confession. 
I didn’t realize that I was force-quitting apps on my iPhone and iPad, nor did I realize it was not a good thing. My first iPad was inherited when my hubby passed away, and I’ve used it the way I saw him use it – and that behavior has continued until I read this thread. 
The good news is that I’ve stopped this behavior. I open apps and leave them alone (background refresh is off). I now find that I can go several days before having to recharge my ithings, instead of nightly recharging. My iPad has gone 4 days since its last charge, and that’s with gmail, a card game, facebook, camera, photos, messages, and instagram running. Two apps that auto quit on their own are 1Password (security I’m sure), and the app for the local Fred Meyers (Kroger). Move it to the background and I have to relaunch it.
I don’t use as many apps on my iPhone, but I have now messages, the phone, camera, and photos all running – again with background refresh off. Oh, and it’s way easier to snap a photo in a “hurry up before the bird moves” moment since the camera is always ready. I guess I’m never too old to learn something new. Love this place.