I still think you're stuck in an old mindset with regards to the app switcher. It's just apps sorted by how recently they were used. You're not meant to scroll endlessly. How far back people like to go will vary by user (for me it's about 5 apps), but you're not meant to go through the whole list the way you would on OS X. Killing apps from the task switcher wastes battery and makes apps slower to launch since they are purged from memory.
You're also in the wrong mindset. If you've used an app 1 hour ago and have used 4 other apps in that time frame, that app you used an hour ago more than likely got booted from ram. You would no longer get those battery/quicker launch benefits, it would have to fresh launch again anyways. So in the end it makes the "battery/launch" point moot.
There are benefits to manually closing out apps you
do not frequently use.
1: A closed app has zero chance of getting stuck or hung on a process (which probably happens more than people realize) 8.4 Music app is a good example of causing issues if left "open", in the switcher. Closing it totally eliminated that issue.
2: Odds are if you don't use that app multiple times an hour, every hour, it has been kicked from ram and all that benefit is lost.
3: Some apps will run indefinitely regardless of background refresh or not. (Facebook is a prime example of this.)