All the events come to an end. And also Drupal Dev Days. We know that it is hard, but you have to get over this. Here, you have some tips which may help you to bear it better.
After Drupal Dev Days, you might mail or phone with your Drupal colleagues in order to check how they are.
Doing research into Drupal
You can read posts or update about new modules or tools of your favourite CMS.
Collaborating with drupal.org
You might make your contribution through snippets or commits for Drupal core.
Planning next events
You can check the calendar and check when and where the next Drupal event is.
Being updated about Drupal news
Blogs, Twitter and other social networks are a good resource of information where you can check all the news.
Attending talks about Drupal in your city
Going to talks of local groups in your city or town is a good way to know the newest about this CMS.