Collaborative learning has proven to be a successful method in traditional classroom settings. Computer-supported collaborative learning (CSCL) is regarded as a new paradigm in educational technology. Nevertheless, in the context of infrastructures for lifelong learning, little attention is paid to collaboration. We provide an analysis of lifelong learning with respect to collaborative learning. In order to support the variety of collaboration modes and learning methods in lifelong learning scenarios, existing approaches to learning infrastructures must be extended in a number of directions, e.g. with respect to user management, collaboration management, communication/collaboration functionality, support for (transitions between) different learning modes, and awareness of peer learners. We introduce our approach to an infrastructure for collaborative lifelong learning, which is based on integrated collaboration functionality, transitions between different learning modes, and a scalable standards- based architecture. We sketch two implementations of this approach in an internal as well as a multi party distributed setting and report first experiences.