Hello,

Is it somehow be possible to add an end-date in the members module after which a user account status will become non-active?

[KK]

Not out of the box, I'm afraid.

You can do that by using a simple logic:
For example, you create a text editable in Members template called 'Start date'. On registration event you write into this field the current date (like 'date("Ymd")' in PHP) and add to it subscription's longevity.
Than in profile template type a condition <cms:if>, if current date is more than the date in this field, unpublish member's page.