Preface: people have different kinds of hair and so what worked for me might not work for you.
The last time I had a haircut was a bit more than 4 years ago, so my hair is pretty long. I don't do anything except brush, wash, and condition my hair regularly. I brush it every day, wash+condition every 2-3 days. Washing every day can be detrimental, as it strips away the natural oils that coat your hair. You have to find a balance that works for you so that it's neither dry nor hella greasy. For me, every 2-3 days is that balance.
Beyond that, I don't do anything with it. I would say brushing is the biggest part so that it doesn't tangle and clump (particularly if you have dense hair growth like me). For reference, these (pics)[https://imgur.com/a/kLol4wb] are at 3 years and 4 years, respectively.
TL;DR: basic care goes a long way