Answer, is it relevant to use DLF?
The simple answer is no. The wave cycles applied to any flowline or related lines is not just the theoretical wave cycle for any one year. The wave cycles are recorded for no of years and the worst case is summed for different wave heights. You can notice the maximum no of wave occurs at 0 - 1 meter level. However the applied cycle which is calculated as the summation of different heights at Tree terminal points, which itself is conservative approach to evaluate fatigue of the line. In my opinion the DLF is not required.