For many years, studies have shown that undergraduate research experiences have numerous positive effects on students. This study seeks to determine if students get more benefit from having multiple undergraduate research experiences. Specifically, this study considered how students' self-efficacy and STEM belonging changed as a result of multiple experiences and how students' perceptions of the mentoring they receive related to the growth in their self efficacy. In-depth interviews produced several case studies that outline specific benefits students gained from having multiple undergraduate research experiences. Faculty interviews enlightened the research related to the types of undergraduate research offered in various colleges and universities. Results indicate that students do benefit greatly from having multiple undergraduate research experiences. Self-efficacy and STEM belonging are significantly higher for students who have had multiple experiences versus those students who only had one experience. There is also a correlation between the instrumental mentoring students receive and the development of their self-efficacy. Students shared the excellent benefits they gained from having multiple undergraduate research experiences and the life-altering consequences of instrumental mentoring.