As per default value in phpMyAdmin session timeout after 1440 seconds & generally we are getting following message
No activity within 1440 seconds; please log in again
You can add one line code into config.inc.php of your phpMyAdmin & extend login time as you want to save some time.
$cfg['LoginCookieValidity'] = 8 * 60 * 60;
In above example we have set to 8 hours – That variable takes time in seconds so we have put 8[Hour] * 60[Min] * 60[Sec]
We can extend session via php.ini file but it will affect to entire server & all sites setup in the server so above is best way