it would be nice if we control the visible steps for the labels
http://teethgrinder.co.uk/open-flash-chart-2/doxygen/html/classx__axis__labels.html
only show every 20th label
$chart->x_axis()->labels()->visible_steps(floor(scalar(@values) / 20));
this may be another way to control the spacing
http://teethgrinder.co.uk/open-flash-chart-2/x-axis-labels.php
$chart->x_axis()->labels()->steps(floor(scalar(@values) / 20));