CSS classes text field should allow longer value

The CSS classes textfield has a 'maxlength' of 255.

  $form['css']['css_classes'] = array(
    '#type' => 'textfield',
    '#title' => t('CSS classes'),
    '#default_value' => $edit->settings['css_classes'],
    '#size' => 40,
    '#maxlength' => 255,
    '#description' => t('Adds CSS classes to the "styles" droplist. Format is: &lt;title&gt;=&lt;class&gt;;<br/> Example: Header 1=header1;Header 2=header2;Header 3=header3 (note: no trailing \';\')<br />Leave blank to automatically import list of CSS classes from style sheet.')
  );

For more complex sites this isn't enough space to enter all the classes and getting the list made from the CSS file isn't an option for me. Is there a reason for this? Can it be a textarea without a limit?