According to this source, the fastest official times for the Porcupine Mountains Loop range from 5 to 6 hours, though a sub-5 finish is absolutely within reach with proper training. Though you must complete the official circuit seen here to be recorded on the registry, those less concerned with their times have the option to shorten or lengthen the route as needed. For instance, one shorter run or day hike is to link Beaver Creek, Little Carp River, S. Mirror Lake, and Summit Peak.

Leashed and well-mannered pets are allowed in the Porkies, making a great alternative to running the Greenstone Ridge Trail (GRT) or Minong Ridge Trail on Isle Royale NP. Water is also abundant along the trail, though it should be sufficiently treated or filtered first. There are no developed facilities or potable water on trail, though the Michigan DNR makes note of "rustic restrooms" at the Lake of the Clouds Scenic Overlook.

One feature that makes this circuit great is its versatility. The loop as mapped here begins from the trailhead for Summit Peak Observation Tower, one of the best and most-visited views in the park. Should something go wrong early on, or if you're simply looking for a shorter loop, Mirror Lake is the gateway into the main portion of the route. It makes a great day hike or running destination when paired with Summit Peak.

Sources: https://fastestknowntime.com/route/porcupine-mountains-loop-mi