Closing Apps in iOS?

If you're using an iPhone or iPad running the iOS operating system, should you close an app after using it, or periodically close all apps that you've opened during the day? Here are two articles that say no:

Prior to reading the above I had thought that apps, once used, remained running in the background and consumed a slight bit of operating memory. Apparently this is no longer true. Background apps, it seems, are 'frozen' and no longer consume operating memory.

This is good to know, and I'll not worry about closing background apps.

Jim Hamm