After so long , still no reply, does apple smart enough in manage the memory , so it will not have problem even program all are open in the background and no issue at all.
The iOS has built in background processes called "Jetsam" (I think its that one) that closes down opened/unused apps to free up memory.
I don't even other closing down my apps anymore. And I know this is working cause under Console, it shows it closes down several apps that I haven't used for a while.