100% up to the GM as makes sense for the setting/campaign and the way things work in the world.
Some GMs allow it for the first 24 hours without any resist rolls, and then after the player would have to charm again, and at that point it gets the resist rolls.
Some GMs might allow it for the first round, and then resist rolls start.
It’s important to remember that not all creatures created this way will be hostile, just as some will not be friendly.
For me, as a GM, it would depend on the feel of the campaign, and the nature of the character doing the animation. I’d either allow it for 24 hours, or maybe allow the resist rolls to not happen until after a minute or an hour. It would probably also matter what the creature is that they are animating.