In general, you get more split ends the longer your hair gets, but it’s possible to keep a beautiful, long hair with very few or no split ends.
Split ends are the result of the deterioration of the hair cuticles, so the internal part of the hair (cortex) starts to be visible. It happens because, differently from skin, the hair (except for the scalp and follicles) is a dead structure. In other words, the damage to the hair accumulate with time. To understand hair as a dead structure, think about when you cut your hair. You don’t feel pain, right? (At least no physical pain, but maybe some emotional pain :-)). On the opposite, if you cut your skin, immediately you feel pain.
To understand better how the damage to the hair accumulates with time, see below pictures that show amplified images of the same hair fiber, the picture on the left shows the hair near to the root and the picture on the right shows the end part of the same hair fiber. See that in the first image the hair cuticles are very aligned, in the second picture the structure is significantly damaged.
Those damages can be caused by many reasons (excessive combing, chemical treatments, exposure to sunlight, etc). To avoid them completely is very difficult (especially if the hair is too long), but it’s not impossible.
One thing that helps significantly is to apply conditioning leave-on products (e.g. serum, hair creams, etc) constantly in the hair ends, especially when the hair is still short (or after a hair trim). Many of those products will help to keep your hair stronger and more protected from damage. The key point is: don’t wait for the hair to have split ends to take care of them. In opposite, have more a prevention approach to avoid split ends!