Changing the Font Size on the Axis Label seems to work, when the number of datapoints in the series is low. If there are too many datapoints, the specified font size is not applied. Is this a known issue? Is this by design?

I wanted the Font Size to be readable, so I went to the code behind and set the size for the font, but that doesn't seem to work. The formatting doesn't get applied, but the Units gets set correctly. Am I missing something? Here is the code:

            var axe = new Infragistics.Windows.Chart.Axis();
            axe.Label.Format = "{0:MM-dd-yy}";
            axe.Label.Angle = -45;
            axe.AxisType = Infragistics.Windows.Chart.AxisType.PrimaryX;

            axe.Label.FontFamily = new FontFamily("Arial");
            axe.Label.FontSize = 20.0;
            axe.Label.Foreground = System.Windows.Media.Brushes.White;

            if (data.History.Count > 10)
                axe.Unit = data.History.Count / 10;
            xamChart1.Axes.Add(axe)

Could you please explain what is going on? I should clarify that I am using the DateTime on the X-axis of the chart and I checked my data to ensure that all dates are valid.