Increasing the milking frequency of dairy cows to 4 times a day (4×) in early lactation increases milk yield both during the increased milking frequency (IMF) treatment and after the cows are returned to 2× milking. Modifications of this approach have been examined to maximize production and determine the most efficient practice for producers. The aim of this study was to investigate the effect of duration of early lactation IMF on milk yield (MY). Twenty-one primiparous and multiparous Holstein cows were assigned to have the right udder half milked 4× (0300, 0600 1500 and 1800) for 10, 20, or 40 d (n = 7), and the left udder half 2× (0300 and 01500). Udder-half milk yields were measured at 10, 20, 40, 60, 120, 150, 180, 210, 240, and 270 d of treatment, and yield differences per day between halves were calculated. Data were processed through the GLIMMIX procedure of SAS (SAS 9.4; SAS Institute, Inc., Cary NC). For 10-, 20-, and 40-d treatments, mean udder half differences (4× − 2×) through 270 d of treatment were calculated for MY (0.87, 1.75 and 4.09 kg), fat yield (13, 61, and 136 g) and protein yield (28, 52, and 117 g). Only the 40-d treatment differed from zero for each yield, including solids-nonfat, lactose, and somatic cell count (P < 0.05). Interactions of treatment by DIM and treatment by parity were not significant for udder half differences of any measures (P = 0.36). The MY difference was different from zero on d 20 for the 20-d treatment, and on d 10, 20, 40, 180, 210, 240 and 270 for the 40-d treatment (P < 0.05). Fat yield difference was different from zero on d 10 for the 20-d treatment and d 10, 20, 60, 120, 180, 210, 240 and 270 for the 40-d treatment (P < 0.05). Protein yield difference was different from zero on d 10 for the 10-d treatment, on d 20 for the 20-d treatment, and on d 10, 20, 40, 180, 210, 240, and 270 for the 40-d treatment. Overall, the 40-d treatment resulted in greater milk and component yields. Supported by Agriculture and Food Research Initiative Competitive Grant no. 2017–67015–26538 from the USDA NIFA and project 683 of the VA Agricultural Council.