If I substitute coconut oil for veg. oil in brownie mix, should I still cook the same amount of time?

I have substituted both coconut oil & coconut butter in baking, with great results. If you end up liking the results, some brands recommend - for better texture - a mix of 2/3 coconut butter and 1/3 coconut oil for baking.

Yes, I don't think the timing will change. A friend of mine did the same thing when he made his orange cake and the result was fabulous.