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.
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.