I trim my hair regularly, I have also cut my hair countless numbers of time. When I am tired of it, or when I want to change my looks, or when I was transitioning to natural hair, I had to cut the tips of my hair in order to be all-natural.
Cutting your hair is optional and can be done when and where ever you want it. Some religion does not accept a woman cutting her hair, so you cut your hair can be affected by your religion or personal belief. People have different reasons why they cut their hair. You might want to change your hairstyle to a shorter hair or just like being on a low cut.
There is no general rule as to when exactly you should have a haircut. There are some factors that need to be considered. This is because our natural hairs grow very differently; some grow faster than others. And it also depends on the type of hairstyle you like to keep. Some like a shorter style, which means cutting it every three weeks is still okay. Like I said earlier, this is not for everybody, even if you like shorter styles. Yours might be every four to six weeks if you notice your hair does not grow very fast.
If you are keeping a mid-length hair, you also need a trim, but four to five times a year is still okay. In addition to this, proper treatment is strongly advised. Also, if you are keeping a very long hair, it is usually advised to cut it once it is getting longer than your shoulder. For this type of hairstyle, your hair can easily get damaged by split ends, which means you need to take good care of it.