Assuming it's either on all AA metal or an all-partner award, you are allowed one stopover, which you could take in DFW, where you can stay for as long as you want (as long as your ticket in still within the 12 month limit, I believe), at no additional cost in miles. If you are not using it as your stopover, maximum connection time rules apply, which are in the aforementioned link, and dependent on the type of award.