Through social media you can stay in touch with your students after the course is finished. You can do so in a closed group or in a more open manner.
Have a look at the example of a closed group on the social medium ‘Facebook’ under the tab ‘cases’. Under the tab ‘learning more’ you can find a manual on how to make a group on the social network site LinkedIn.
The advantage for your students is that after the course, they can still ask you questions. The advantage for you is that they keep you posted about their working experience.