I can walk out my door and easily run 30 miles at sub 7;30 pace any day of week but my fast speed comes and goes . I’ve been known to have a couple rough weeks the What’s the cause of this? I am shooting to run sub 2:30 next spring but think based off that I could work myself down to sub 2:25 if not faster. In 2017 I ran 22 miles at 9pm at 8 min pace the following morning at 8am ran a road 50k time trial in sub 3:20. Am I meant to do ultras?