This longitudinal study investigates how auditory acuity and the amount of second language (L2) input lead learners to shift L2 cue-weighting strategies towards native norms in an immersion context. Thirty Mandarin-speaking students were tested on Spanish lexical stress perception upon arrival (T1) and before leaving Spain after one academic year (T2). Due to cross-linguistic influence, the learners placed more weight on pitch for stress perception, unlike Spanish natives, who relied more on duration. However, at T2, the learners upweighted the duration cue, suggesting a potential L2 cue-weighting shift. At the individual level, more L2 input helped learners with lower pitch acuity shift towards a native-like cue-weighting strategy, whereas those with higher pitch acuity showed the opposite pattern. The results highlight the persistent influence of L1 prosodic transfer and the interaction of cognitive and experiential factors in reshaping L2 perceptual categorization, which underscores the importance of individual differences in L2 speech acquisition in naturalistic settings.