Topic modeling has been applied to several areas of software engineering, such as bug localization, feature location, triaging change requests, and traceability link recovery. Many of these approaches combine mining unstructured data, such as bug reports, with topic modeling a snapshot (or release) of source code. However, source code evolves, which causes models to become obsolete. In this paper, we explore the approach of topic modeling changesets over the traditional release approach. We conduct an exploratory study of four open source systems. We investigate the differences in corpora in each project, and evaluate the topic distinctness of the models.