Hmm, I beg to differ. I am getting excellent battery life. But (I think) your claim makes some sense.
Well that depends on your particular case. What I stated is a matter of fact, as apple has designed it. Its possible that you are indeed closing apps that were running in the background. But that's a co-incidence, not necessarily based on the MRU list. you will achieve the same effect, by switching off notifications and background refresh for those apps.