It is often said that if you trim your hair that it will grow faster. The truth is that your hair does not grow faster as a result of trimming. Your hair grows from your roots and when you trim, it affects your ends so technically trimming actually makes your hair shorter.
Trimming does help your hair to not only appear healthier, but to stay that way also. When you avoid trims, your ends continue to split up the hair shaft. When that happens your hair does become damaged, and when you finally do get that desperately needed trim, you end up having to actually get a drastic cut.
When you trim on a regular basis, you stop the ends from splitting up the hair shaft. This helps you to retain length. Bottom line, trimming your ends help you keep more length, and the more length you keep, the longer your hair will be.
I recommend trimming your ends every three months. If you do not take proper care of your hair then you will need to trim much sooner. Although you can not fix split ends, you can prolong them from splitting as fast. Be sure to wrap your hair or roll your hair up every night and tie it up with a silk scarf (like this one). Also, you can moisturize and seal (get full tutorial here) your ends to help them not split as fast by using products like the by L. Jones Silky Growth Oil (sealant) & Leave-In Conditioner (moisture).
Remember that nothing will stop them from splitting altogether but these things will help you retain more length. Lastly, be sure to let a professional trim your ends. If you are concerned about your hairstylist trimming too much, ask them to turn you around to the mirror and allow you to see the process.
Check out the video here!