I'm curious as to how two polymorph spells with different durations would interact.
The rules for polymorph spells (https://www.d20pfsrd.com/Magic/#TOC-Transmutation-Polymorph) reads, in part,
"You can only be affected by one polymorph spell at a time. If a new polymorph spell is cast on you (or you activate a polymorph effect, such as wild shape), you can decide whether or not to allow it to affect you, taking the place of the old spell."
What I want to know is what the phrase "Taking the place of" means in the following situation:
My Wizard PC would like to use the Polymorph Any Object spell to become a medium sized dragon, as per the spell Form of the Dragon I, with a permanent duration. Now, there may be some times when becoming humanoid again would be convenient. If Alter Self was cast, I understand that I can choose to have the Alter Self spell override the Polymorph Any Object.
What I need to know is, does the duration of permanent on the Polymorph Any Object dragon form continue after the Alter Self spell expires, or is it gone?
I imagine there exist someplace rules for explaining spells with different durations overlapping, but I cannot find them.