How to increase default Drupal minimum cache lifetime options to a custom value?

Question

Currently the max page cache age is 1 day. I would like to icnrease to 1 year. How can I do that?

These settings are located at /admin/config/development/performance

• "Minimum cache lifetime"
• "Expiration of cached pages"

Boost had a patch http://drupal.org/node/326683, wonder if this somehow could be applied for the core cache.

Answer 1

Just set the variable 'page_cache_maximum_age' using variable_set in custom module to the value 31536000

variable_set('page_cache_maximum_age', 31536000);

If you install the Devel Module there is a page for viewing and editing variables.

Above is a quick fix. If you want to do a perfect way then you need to form alter the "system_performance" form and change the option of below field.

  $period = drupal_map_assoc(array(0, 60, 180, 300, 600, 900, 1800, 2700, 3600, 10800, 21600, 32400, 43200, 86400), 'format_interval');
  $period[0] = '<' . t('none') . '>';
  $form['caching']['cache_lifetime'] = array(
    '#type' => 'select',
    '#title' => t('Minimum cache lifetime'),
    '#default_value' => variable_get('cache_lifetime', 0),
    '#options' => $period,
    '#description' => t('Cached pages will not be re-created until at least this much time has elapsed.')
  );
  $form['caching']['page_cache_maximum_age'] = array(
    '#type' => 'select',
    '#title' => t('Expiration of cached pages'),
    '#default_value' => variable_get('page_cache_maximum_age', 0),
    '#options' => $period,
    '#description' => t('The maximum time an external cache can use an old version of a page.')
  );

Answer 2

If you don't want to write a custom module, you can also set these values in your site's settings.php file:

$conf['cache_lifetime'] = 31536000;
$conf['page_cache_maximum_age'] = 31536000;

These values won't show up in the /admin/development/performance screen, so if you need to check the values in force, you can use drush:

> drush vget cache_lifetime
> drush vget page_cache_maximum_age

Or, go with @Anil-sagar's suggestion and implement an override to the system performance form.