Myth: Getting constant trims promotes hair growth. Most stylists recommend trims every six to eight weeks to keep split ends at bay (which truthfully, they do). But how would that promote growth exactly? Jen Atkin, the Clear Scalp & Hair Celebrity Hairstylist who works with long-haired beauties like Jennifer Lopez and Jessica Biel, says the best way to hold onto and promote length is with fewer trims (every three to four months) and a few additions to your routine.