I like using Ubuntu desktop when doing development work but I find that the default screen lock timeout settings can be a bit annoying.

If you want to extend the amount of time your screen is inactive before it times out then this is how you do it.

1. In the top right of your desktop click the icon  and select System Settings.

2. In the settings select Brightness & Lock

3. In here, change the setting to whatever is appropriate for you then click the x in the top left.

4. That should be it. Let me know if this worked for you or not.