Shocking. Still searching for where it says get weekly haircuts.
MCO 1020.34H 01 MAY 2018
(1) Hair
(a) Hair Length. Hair will be neat and closely trimmed. The hair may be clipped at the edges of the side and back and will be evenly graduated all the way around the head (blended or faded and not edged as an outline) from zero length (skin) at the hairline to at least the top orifice of the ear circling around the back of the head, where it may then extend to the maximum hair length. Hair will not be over 3 inches in length fully extended (an extended hair, not the style, determines proper length) on the upper portion of the head. The bulk of the hair shall not exceed approximately 2 inches. Bulk is defined as the distance that the
hair protrudes from the scalp when styled. The back and sides of
below the hairline may be shaved to remove body hair.
1. Sideburns will not extend below the top of the
the ear, as indicated by the line A-A' in figures 1-1 and 1-2. Sideburns will not be styled to taper, flare or come to a point. The length of an individual hair of the sideburn will not exceed 1/8 inch when fully extended.
2. No male Marine will be required to have his entire hair length clipped to the scalp except while he is undergoing recruit training or when such action is prescribed by a medical officer. This does not prohibit a male Marine from having his hair clipped (or shaved) to the scalp if he so desires.