I'd wait until early tomorrow morning, but that's just me. It will just be fresher that way and that way, I don't worry about the whipped cream de-stabilizing on the cake overnight. Whenever I'm using whipped cream for a frosting, I do the morning of the day I plan to serve it. Put your bowl and mixing utensils in the freezer overnight. Not the cream, just the bowl and utensils. It will help whip the cream faster...but you probably already knew that.
Again, this is just my opinion.