ME workout typically comes in towards the end of your training cycle when you move to event-specific training. For e.g. I am following the 24-week mountaineering plan and ME (Z3 Weighted Climb) is after I have gone through the Transition and Base period.
I would recommend completing your Base period and then adding ME workouts, unless you have a trip coming up shortly.
You will find this article on Muscular Endurance helpful. Read ME Caveat.