Cache Lifetime and cron

The lifetime is handled on the php side. For http caching, if there are not any directives that will handle this for your http server, you would have to run a cron. I would recommend an actual cron job and not wp cron. Somthing like this would do the trick:

$cacheDir = '/your-document-root/gator_cache'; // gator cache directory
$time = time();
$ttl = 14400; // 4 hours
$directory = new RecursiveDirectoryIterator($cacheDir);
$iterator = new RecursiveIteratorIterator($directory, RecursiveIteratorIterator::SELF_FIRST);
$cacheFiles = new RegexIterator($iterator, '~index\.(html|gz)$~');
foreach ($cacheFiles as $file) {
    $path = $file->getPathName();
    if (($time - filemtime($path)) > $ttl) {
        printf("Removing cache file %s\n", $path);
        unlink($path);
    }
}

In the next update, will probably have the http tab generate this script with the appropriate ttl and cache dirs populated for better http caching.