I need sounds to feel good early on to stay creatively excited, so I use pre-mixing to get them tonally and characteristically into the right general place as the idea develops. I want each sound to clearly communicate its role and keep me inspired without getting lost in technical details too soon. Once the idea is fleshed out, I go back section by section and mix as critically as possible. At that point, I either rebuild a detailed sound from scratch to replace the placeholder, or I adjust the original sound upstream.