Professional learning and growth for teachers is essential for effective teaching and the learning of students. Teachers receive formalized professional learning at the beginning of their careers through structures such as teacher education and induction programs. Beyond the novice years, professional growth opportunities for teachers vary and can be lacking in stimulation and value towards impacting practice. Given the negative impact of neoliberal forces and the current state of K-12 education in this post-pandemic era with teachers, students, and systems struggling, professional learning and support for teachers is especially vital. Teachers leaving and retiring are increasing, and the new teacher pool is extremely shallow. Understanding the support and growth opportunities that teachers need can help mitigate this crisis. While pre-service and novice teachers are extensively researched, much less is known about the experience of veteran teachers. This qualitative case study examines the careers of three veteran teachers, their professional experiences and how they have developed their conceptual frameworks for practice. This dissertation sheds light on what happens when teachers have been intentional about managing their own growth and learning with the assistance of mentors and a network of support despite many challenges and difficulties to overcome. Informed by case study and narrative research methodologies, this study examines how the three veteran teachers are shaped by the supports and challenges they experience. Their stories and the case study research provide insight on ways that teachers can optimally develop. The first major finding of this study highlights the importance of mentorship throughout the teachers' careers, including having mentors as novices, finding "unofficial" mentors through the years, and benefitting from being a mentor to colleagues. The second main finding of this study shows the how collaborative networks of support are protective factors that foster teacher development. All three teachers intentionally sought out and even created spaces where they can learn with others. The third main finding looks at how reflective practices enhances the learning and development of the three teachers, nourishing both on individual and group levels, offering a range of benefits and positive outcomes. Implications of these findings are explored for how K-12 and higher education systems can more optimally support teacher growth across their careers and how conditions can be created to encourage teachers to be more agentic and intentional in leading their professional learning journeys. Future directions for research on teacher conceptual frameworks for practice building and optimal development are imagined. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]