Despite social media's ubiquity in modern life, research on some topics related to educators' use of social media for professional purposes remains underdeveloped, such as how use may change over time. This study explores educators' self-directed learning through social media by comparing change and continuity in how users contribute, interact and converse in two teaching-related subreddits, r/Teachers and r/education. More than a million Reddit contributions spanning three-and-a-half years comprise the dataset: 696 660 contributions to r/Teachers from 55 148 users and 339 618 contributions to r/education from 43 711 users. Learning ecology and affinity space concepts frame multiple methods of analysis, including quantitative measures of individual contributions, content interactions and social interactions, as well as qualitative content analysis of top posts and responses. Findings are discussed in light of the literature as change and continuity in Redditors' participation patterns in the two subreddits suggest distinct spaces for distinct purposes. This study offers a starting point for further work to understand the opportunities and challenges of self-directed learning in open and complex social media spaces.