As generative AI systems like ChatGPT become integrated into daily routines, understanding how different users engage with these tools over time is essential for designing future information services. This paper presents an empirical user study examining ChatGPT usage patterns across a diverse set of 38 participants. Using exported chat histories, we analyze over 82,000 prompts spanning up to 21 months per participant. Our findings reveal distinct interaction behaviors tied to age, gender, and time of day. Notably, older users exhibit stronger work-week patterns in usage, while women show higher activity at night. These results highlight the roles generative AI plays in users’ lives, extending beyond productivity into moments of reflection, support, and multitasking.