It depends. I am not sure if swiping away closes them either or just suspends them where they no longer use ram or CPU. It's one thing i hate honestly about mobile OS. I prefer to close programs when I'm done with them, and I am not so happy turning all of that control over to an operating system. I like to feel like I have control over my device.
Samsung Galaxy Precedent (rooted, AreaRom 3.4 , sd-ext w/ 3.65GB internal space)
Kindle Fire (1st Gen, rooted, AOKP JB 4.1, Nova Launcher)
Samsung Galaxy SIII 4G LTE (rooted, Carbon ROM)