When should I consider utilizing a hair mask to effectively enhance the vitality and luster of my hair? Is it imperative to integrate this nourishing treatment into my hair care regimen only after a particularly harsh environmental exposure, such as an intense sun exposure or a swim in chlorinated water? Or would it be more beneficial to use a hair mask as a preventative measure on a regular basis, perhaps on a weekly basis, to mitigate damage before it occurs? What specific indicators should I look for that would signal my hair might be in need of this extra dose of hydration and care? Could the texture and overall health of my hair, perhaps becoming increasingly dry or brittle, be warning signs that necessitate this treatment? Additionally, should the frequency of application vary depending on my hair type, be it straight, wavy, or curly, and its unique needs? What nuances should I be aware of?