Depends on the type of paint.
I've had paint literally peel off as the brake fluid touches it and in other instances it has taken a few days.
Just make sure you wash it all off as it will eat any new paint you put over the top
Best thing about it is that it's cheap, re-usable & will not harm the plastic. I've had plastic figures (both poly prop (soft plastic) & poly styrene (hard plastic)) soaking in it for months and no damage to them what so ever.