I agree with part of that, Waffle... organic, non-geometric details like terrain tiles will look better when sampled down. But please understand that this is merely an illusion of detail. Detail and smoothness of image are two very separate things in this case.
The point I am trying to make is mostly about 1-pixel objects: look at octavius' example up top... Some of the 1-pixel rivets on the 2048 version actually become 4-pixel rivets. This is not optimizing detail; this is creating an illusion of detail. Working 2:1 will help on large areas (like noseart), but not when you are trying to save specific single pixels.
Remember also that the game is going to add yet another resampling of all those pixels by mipmapping, etc. If you think something looks blocky on a skin, check it out in-game before deciding to work it much further.
Don't get me wrong, I have nothing against people working 2:1. I just want to dispel the myth that it creates extra detail. It does not. In many cases I work 2:1 on a separate file for things like noseart, wheels, engine faces... but as a whole work 1:1 because I think it's actually easier. You could try adding the rivets after you've resized the skin.