I have a favorite jambalya recipe. I usually saute the trinity (celery, onions, green peppers) for a short while before adding garlic and then a longer while later I will add my Cajun seasoning. For some reason the other day I did it differently and added my Cajon seasoning to the oil before adding the trinity and garlic (like I do when making Thai curry - adding the curry paste to the oil to start the cooking). I was surprised to find my final dish at the end was far less spicy (less hot) and there was less of the flavor from the Cajon seasoning. That surprised me. Slightly less spicy would make sense but this was WAY less spicy. I used the normal quantity of all ingredients so that wasn't the cause of the difference.
EDIT: DIshes made 3 days apart with spices that have been stored the same length of time (months+).
What is going on?