Background. Teachers' job burnout is an ongoing concern. A 2017 survey of 18234 Australian teachers showed 60% reported unacceptable stress (McGrath-Champ et al., 2018). Mid-career teachers have been an under-researched group, although there is much to learn about what personal and environment factors can sustain them.Aims. We followed the evolution of teachers’ professional striving and wellbeing in response to workplace demands and supports from early to mid-career, in a unique large-scale longitudinal study, to ask:1) What is the nature of teachers’ striving/wellbeing profiles in early and mid-career? 2) What is their evolution from early to mid-career? 3) To what extent can perceived excessive demands and leadership support predict profile changes? 4) Do teachers’ striving/wellbeing profiles matter for their retention and professional engagement?Design. The study is from the ongoing Australian Factors Influencing Teaching Choice project (FIT-Choice; www.fitchoice.org). Surveys asked about teachers’ professional striving, wellbeing, engagement and retention from early (M=3 years teaching) until mid-career (M=10 years). We included 414 retained teachers who had been teaching when they answered the first survey (primary n = 171, secondary n = 243; 79% women). Latent transition profile analysis (LTPA) examined changes among five striving/wellbeing profiles: Sparing, Good health, Ambitious, Burnout and Wornout. Impacts of excessive work demands and supportive leadership were examined using odds ratios. Consequences were examined with chi-square for retention, and a maximum-likelihood three-step approach for professional engagement. Key Findings. LTPA showed 72% of teachers remained in a same profile from early until mid-career. Of concern were the high proportions of Wornout and Burnout teachers who remained in those risk profiles: 72% for Wornout and 51% for Burnout. Initial Burnout and Wornout profiles were overrepresented among those who subsequently quit teaching. Of the 28% who changed profiles from their early to mid-career, most movers from maladaptive types underwent a recovery transition to a more adaptive profile. Perceived excessive work demands made it less likely for Burnout and Wornout teachers to recover. Supportive leadership increased the chances of transitioning to an Ambitious profile. The Wornout profile exhibited the poorest, and Ambitious and Good health profiles the most positive professional engagement by mid-career. Implications. Better understanding of the evolution of teachers’ professional striving and wellbeing can help school leaders, and teachers themselves, to identify those at risk and sustain teachers’ engagement and thriving. Policymakers and school leaders should address an increasingly pervasive culture of excessive demand.