Due to a general development in education brought about by democracy, Portugal has witnessed tremendous development in Higher Education (HE) since the beginning of the 1980s. Nevertheless, the percentage of graduates among the Portuguese population still ranks far below most European countries. This is why academic performance in HE 1st cycle matters so much and warrants a careful analysis of the main determinants for failure. Life cycle theories are taken as our main theoretical framework. This paper worked with Individual semi-longitudinal data on ISEG students retrieved from the School Pedagogic Observatory Database. The number of attempts until the successful completion of two 1st year disciplines (Mathematics I and Economics I) was the chosen "proxy" for failure. A discrete-time survival model was used. To deal with the unobserved heterogeneity a random variable was introduced - frailty - in the linear part of the model. A normal distribution was assumed in the estimation of a logit panel data model with random effects. As expected, students took longer to achieve success in Mathematics 1 than in Economics 1. Gender, degree course, the track followed in upper-secondary, and the application mark to enter HE are among the significant determinants of success in Mathematics 1 and Economics 1.