When I used to be an editor there would be a final sound pass done after me mostly for top quality music, dialogue tweaks, etc. A lot of my sound effects though ended up making it in the final product depending on the quality and how well they matched up. I very quickly found myself getting excited and randomly recording strange noises in public - that squeaky fan in the parking garage you might not normally notice might in fact be making some super unique mix of resonances that can be manipulated into something really cool!