"For rendo 1024 x 768 at 72dpi I use totally different values for my client work, usually in inches and at 300 dpi."

Well that doesn't tell us so much does it, for the ones iín inches and dpi was perhaps some simple logos? Without seeing what that is rendered size tell nothing.

Here is a render from 00AngelicDevil00's "First render of 2011", rendertime was 58 hours.

http://www.renderosity.com/mod/gallery/index.php?image_id=2155735&user_id=577773&member&np

 But she doesn't tell what was the rendersize! What I want to know is, is it possible to render pictures of such complexity in 4000x3000? And what will the rendertime be?