I guess there are 2 theories to take it from:
1. Subtype preference is not changeable....one will naturally have a preference there too....and one must accept it to validate one's own existance in a harmonious interpersonal way whether one is aware of it or not.
2. Subtype preference is changeable.....it is just a temporary preferential stage....as we encounter new people or new situations we develop enough internal frameworks to tilt the lever the other way.
who knows for sure.
I like to think it's #1 for good reasons and #2 only provides for temporal impressions of change...but hey...that's me.