The longest was probably the vegetarian → vegan pipeline.
My position was that ‘employment’ of animals was humanely possible, if you genuinely treated them like you’d want to be treated.

It was until I read how cows need to basically be kept continuously pregnant, that I realized there was just no way.
I believe, you could have a bite of cheese every year or so, if we don’t do forceful impregnation, but at that point, why even bother?