How can I stop the lock screen locking itself every two minutes? How can I extend the time it takes to turn off automatically? I'm running Jelly Bean v 4.2.2 on a Samsung Galaxy S 4.
Go to Settings -> Display -> Sleep, and you can change the time out requirement from there.
If you want the timeout increased permanently, you can use the hint given in TronicZomB's answer. But keep in mind that display is one one the heaviest battery consumers -- so if you often forget to turn off your display manually, your battery might last much shorter.
A more intelligent approach would be using some automation software like e.g. Tasker or Llama, and have your display timeout set according to your situation. I use e.g. Tasker for that: when one of my reading apps (RSS, eBook, Web) runs in foreground, Tasker increases the display timeout to 3 minutes. As soon as I exit them (another app or the homescreen comes to foreground), display timeout is reset to 30 seconds.
Of course you can adjust those values to your needs. As a side effect, you will be able to automate a lot of additional stuff. For me, Tasker e.g. automatically activates GPS when I start some related app, and deactivates it afterwards (on 4.2, this will require your device to be rooted). It also switches WiFi off when I left home (and turns it back on when I return), and adjusts ringer/audio volumes when I'm in the office, plus more.