To get this when your phone doesn't have the timer lock ''never'' you want to actually use aluminium foil.
Ok so let me explain: You want to place a ca 6x6 alum. foil on your screen then you try to grab a bird with the foil having a finger exactly in the middle and simply let go of the foil, CAREFUL. If you didn't do it right because a bird was slinged, just try again. Also make sure to put the phone on recharge.
Don't ask me how the heck aluminium foil works, I did the same with Angry Birds Star Wars, 10h and 30h cheevo
Also worked but that game crashed but this game, Classic doesn't
About the aluminium foil, how it works I really don't know, have no clue but I can guess it has to do with the effect it have, either warmth or electricity similar to our skin, or a finger. It's actually very interesting. I wish I could say thanks and leave a name because this trick was said from a dude on a faq site. But let us thank whoever this guy was and me for taking time to write this (doesn't take long haha)
So people, hope this helps, it sure helps me since I have Lumia 820 and max lock is 5 min, so the aluminium foil comes in handy in situasions like these