.Conditioner's primary job is to soften and detangle the hair. Most conditioners will also have a specialty purpose like hydrating, repairing, smoothing.
There are also 2 types of conditioners:
-Daily conditioner: This is your regular conditioner that is formulated to be used daily or at every wash.
-Treatment or deep conditioner: These are your power player conditioners that are packed ingredients to address specific needs.
For your daily conditioners you only need to apply them, work them through thoroughly then rinse. However, many choose to apply and let set for the duration of bathing time. This is especially good for long hair that tangles up, and dry damaged hair.
For treatment conditioners they typically have directions to leave on longer, often 10 minutes after being thoroughly worked through the hair.
"Can I leave either conditioner in longer?" Yes! You can absolutely leave them in longer. We often recommend our clients with long, tangly, or dry hair to leave some conditioner in if it's going to be a messy bun day. This allows the conditioner to work longer, and also provides a little protection in the hair. Depending on how much is left in, the hair will likely have to be rinsed, or washed and rinsed when ready to style next.
Conditioner is only working when it is wet. Once your hair and the product have completely dried out, it's just acting as a protective barrier or styling product.
How long is too long? Really the main bad thing that can happen is if you have thick hair that doesn't dry easily and you're wearing your hair up with conditioner in it and it stays wet for multiple days it can cause mold to grow in you hair which can make your hair smell bad and other potential health hazards related to mold exposure. Don't worry that is the absolute worst case scenario, and I have never seen it happen in my hair career, the hair would have to stay wet for a VERY long time for this to happen.