Grainger
Explorer
Uhhhhh what?
I wouldn't.
Actually that's not true. If the PCs wanted to pull off some sort of caper or plan in the throne room while talking to the Prince I might.
"If my players were interested enough to take an hour to talk to the Prince..."
...in the context of using battle mats. I think the discussion was starting to muddy combat and non-combat encounters.
Of course, a non-combat situation can evolve into a combat-based one (or a stealth one, or similar). I was just trying to get an idea of whether some groups use grids for every encounter in case it breaks out into a fight.