Demons and "at will" spell-like abilities.

[Solarious]

Order has nothing to do with it. Chaotic does not mean stupid. CE people usually respect only one measure: power (selfishness + freedom). Demons, as the exemplars of CEness and probably surrounded by like-minded CE exemplars, will try to get every advantage that they can grab so they can stay on top of others... keeping at-will SLA seems perfectly reasonable, long lasting SLA in particular. After all, many Wizards get (Greater) Mage Armor up at the start of the day, because it lasts all day for one casting.

And what Rogue won't keep Invisibility up once they get hold of a Ring of Invisibility?

 

[xmanii]

I think they would, as it is about survival of the fittest. It would be more of a question why they wouldn't have it up in the first place.

 

[pawsplay]

A celestial's magic circle of protection is continuous. If demons were intended to have the abilities continuously, they would be continuous.