The mantra of "never force quit apps that are in the background via the app switcher" really shouldn't betaken verbatim as "never".
If you -never- occasionally clear out the app switcher, eventually all the "cards" for every app you ever opened will clog it up to the point that it's virtually usable. Got 100 apps installed? The app switcher will end up with 100 app "cards" even after you reboot. It becomes way too cluttered.
I think a more workable solution is to clear out the app switcher once a day and force quit an app you know you'll not use again that day.... If you're rebooting once a day like you should. That way, switching between apps will be easier because of less clutter.
There's a bit of missing information from Apple about the app switcher too. If you launch every app you've got, say 100 apps, then reboot the phone, all those 100 "frozen apps" in the app switcher will still remainin on next boot. But they aren't frozen. iOS didnt partially load 100 apps into cache/Ram in the background during boot up. They're just pictures/snapshots of the apps. If you click on one of them, you're loading it up from ground zero. There's no secret cache file in the background that will speed it up or reduce battery drain.
So I say- clear out the app switcher before or after a reboot- so you can actually use it for what it was designed for --- switching apps.
I don’t see the problem with having 1000 apps in the switcher. In my experience I use maybe the last 3-4 apps in the switcher. It’s much easier to go to the homescreen if I want to open something else that’s not currently open in my workflow. I never close apps unless they are misbehaving.