Khawaja.. it is difficult but not impossible for an honest person to do so. Not that I want to indulge in what Islam has to say about this, but yes, it is a condition that a man divides his time/wealth/presents/vacations equally between his wives or face harsh judgement in front of a court and ultimately in front of God. Prophet Mohammed taught that a man who has not treated his wives equally will come on judgement day dragging half his body on the ground and the other half upright. It is that serious, so a man who thinks he can't be fair should think twice before taking such a step.