YouTube vlogging, as a popular genre of ubiquitous social video, engages people in entertainment, civic, and social activities. Although several aspects of vlogging have been studied in media studies and multimedia analysis, the longitudinal angle of vlogging regarding recognition of personal state and trait impressions from behavior has not been yet analyzed. We present a study using behavioral data of vloggers who posted vlogs on YouTube for a period between three and six years. We use online crowdsourcing to collect a rich set of 21 impression variables for each video, including perceived personality, mood, skills, and expertise. Acoustic and motion features are extracted to characterize basic nonverbal behavior. The analysis shows that only a couple of perceived variables, including perceived expertise and perceived quality of audio and video, display weak temporal patterns. Furthermore, we show that the use of longitudinal data helps to improve the automatic inference of impressions for several of the impression variables.