Teacher noticing, a situation-specific part of teachers' professional competence, has gained much importance in the past two decades. The construct is believed to play a crucial role in the transfer of knowledge and skills into professional teaching performance. However, there is little empirical evidence on how the length of teachers' teaching experience affects the development of expertise in teacher noticing. In particular, little research has been conducted on the development of facets of teacher noticing--namely perception, interpretation, and decision-making--as well as the handling of cognitive demands while applying teacher noticing. To fill this research gap, the present study investigates the teacher noticing of master's students, early-career teachers, and experienced teachers in the context of secondary mathematics via cross-sectional comparison. Teacher noticing skills and differences between the three groups are analyzed based on participants' ability to deal with the cognitive demands of an established video-based teacher noticing instrument. The results suggest significant increases in teacher noticing from students to in-service teachers, especially in mathematic-specific areas. Hardly any significant differences were found between early-career and experienced teachers, which suggests a stagnation in teacher noticing skills. However, the early-career teachers showed better performance in decision-making and mathematics-related items as well as knowledge-based items related to recent topics from mathematics pedagogy and general pedagogy. This result emphasizes the importance of knowledge prerequisites for the development of expertise in teacher noticing. It also highlights that expertise development is not directly connected to the length of teaching experience.