This study explores Vietnamese marriage-migrant mothers' changing attitudes toward heritage language (HL) education in South Korea through narratives collected in an interview setting over a period of four years. The findings show that while the mothers placed some value on HL education, they initially prioritized Korean at home because they viewed it as key to their children's academic success in Korea. However, the mothers' perceptions of the value of their native language changed over time, influenced by their increasing awareness of the benefits of bilingualism, their imagined bilingual communities, Korea's increasingly competitive job market, and their children's social and academic experiences in school. Over time, the mothers came to view their minority language as an asset rather than a deficit and thus chose to invest in developing their children's HL skills to position them as potentially valuable bilingual workers in both Korean and transnational contexts. The participants' narratives reflect their view of the minority HL as primarily a socioeconomic resource rather than an identity resource, while the longitudinal study highlights the dynamism and changing nature of language ideologies in relation to HL maintenance.