Fishes are fantastically plastic creatures, capable of altering their morphology, physiology, life-history, and even offspring responses to changes in the environment. A key question in freshwater ecology is how fishes will respond through plasticity to continued changes in climate - especially to predicted increases in the variability of temperature. Here, we describe lessons learned from long-term, multi-generational experiments examining thermal variability's plastic effects in a model organism, zebrafish (Danio rerio). We found that long-term exposure to thermal variability confers relative benefits in a number of fitness-related traits, but these benefits were not without costs. We highlight the advantages of using thermally variable regimes in experiments and discuss important knowledge gaps that remain in the study of thermal variability and plasticity.