When I play anything in 6th partial (

) or lower, I just play it, letting muscle memory find the right partial. But for anything higher, even the F#, I have to hear the pitch in my head before I can play it. F has always been the cutoff, since I was a wee lad; it hasn't moved as I've improved as a player.
Is that everyone's threshold? Do other people even think of notes that way? Is it possible to raise the threshold? Is it a mistake (musically) to rely on it?
I can still be shaky, intonation-wise, on the shortened 7th partial positions. Maybe that has something to do with it?