Depends with me. Sometimes it just happens realy quick. Its on mix down where i can get stumped for a while. I hate been on a track for too long, its the worst feeling when you feel kinda irritated buy how many times you have heard something. My advice would be to work fast and avoid been hypnotised by your own beats. Sometimes I mute the main channels on my track when working on other parts of it, unmuting and checking its still sitting. Then your not having the full thing played over and over. Always ask youself and others what they think. Its always great to have feedback from some one with squeegeed ears 8)