Well, I always maintained when FOs came to me and said "so and so is horrible to fly with ", that they were w**kers before they got 2 stripes, then w**kers with 3, 4 so on. Nothing changes.
As for TREs, they can be split into 2 categories - those with massive experience who want to pass that on, and those who collect ratings because it boosts their ego.
I did once want to be an examiner, but now I feel flying takes up enough of my life without extra stuff to study..