Do I need to think about changes to Earth's rotational axis over time when I consider the causes of seasons?

Yes, technically though, you will be long gone before than but theoretically yes, the seasons will be different whenever it come to the axis.

Explanation:

This is because, considering temperate climates are the result of being closest and most often in path of the sun, it makes them much hotter. If over a long time we calculated that it is possible that the Antarctic would be in the closest position with the sun and the highest amount of time in the sun.

Hope this helps :)