I've a fair amount of experience with Mage: The Awakening, first edition, but it's been several years, and I'm trying to learn again with the new system from Onyx Path Publishing. In the rules on spellcasting it says that you can alter a spell's Primary Spell Factor by using a reach.
I now understand what changing the spell factor is. It applies in cases where I might want to change the spell's primary factor from potency to duration. My question is: Why would I want to do this?
If I can already alter the range, duration, scale, and potency, why would it ever be worth investing one of my limited reaches to changing which factor is considered primary?