IPhone :: Caseless With My IPhone 3GS / Retain Its "Like New" Condition?

After using some sort of removable-for-use case (a leather flip case and a sleeve) for the first two iPhones, I went with a plastic hard case, the Seidio Inncase II, for my iPhone 3GS. I took that case off tonight for the first time in my iPhone 3GS's lifetime and was reminded why I never liked hard cases. The iPhone 3GS looks much nicer without a plastic case, though I liked the peace of mind that a plastic case offers.

Since my iPhone 3GS will be going up on eBay and likely kept with myself until mid-July when I buy my iPhone 4 (I was going to preorder it this week...), I'd like to retain the way my iPhone 3GS looks like new, aside from a hairline scratch or two. I'm OCD with my devices (only setting it down on a soft surface, etc) but I'd like to be "normal" with it for my last few weeks of usage, so not have much regard for where I set my iPhone as long as it won't fall, keep it (alone) in my pocket without any type of sleeve, etc.

Is the iPhone 3GS really durable enough to be in a fantastic condition when an eBay buyer receives it? I've noticed through comparing my sales of the last two iPhone generations with others' sales, an iPhone that still looks new can receive prices of upwards of $100 over other used iPhones.