I always archive both with and without lines when available. I then print out the lineless version for the build, but when building I have the lined version up on screen to show me where the folds should be to shape the part.
Also, whenever plausible, I don't actually crease in the folds. I just allow the card to pull into shape itself. I get better curved surfaces that way. With some complex figures I have found it beneficial to actually print out an unrendered lined version to build alongside the rendered figure. Getting all the experiments, trial runs, failures and corrections done on the blank figure before moving on to the rendered figure. Wastes quite a bit of card and ink I know, but if I were to ever have to worry about the cost of materials, I guess I'd be moving away from the hobby.
Are you really considering building the Dota Illidan Doug ? Did you notice that it is a LIFE SIZE model? Yeah, I'd love to build it too, but I'd have to hire the barn up the road to build it in.
Err, no I don't think this is the paper model. It's just a pic I found on google.