IPhone 2g screen protector?

So I've used a screen protector on all of my IOS devices but I'm becoming increasingly bored of having to change my screen protector on my iPhone 2g because the corners peel up and dust gets in and it doesn't stick anymore etc. Ive seen the videos of people trying to scratch the screen with keys and I am aware of the fact that it is not a very realistic test in the respect that Its not going to be just keys that are a possible scratch threat in my pocket, things like dirt and other things like that are a danger to, I know that diamonds can scratch it so you don't have to tell me that :D.So the question is: how scratched will my screen get if in my pocket or the odd face down on a desk moment? And do I really need a screen protector? What things (besides diamonds) should i keep my screen well away from? And all together, how durable is the original iPhones screen? Ive tried to make this as clear as possible but if this makes no sense tell me and I'll try to reword the question :)