Depending on who you talk to the actual distance of this hike varies from 30 to 40 miles. I put it at 33.5 miles from the trail head at Lamoille Canyon to Harrison Pass. The first 2.5 miles and the last 6 miles are not in the Ruby Mountain Wilderness, everything in between is wilderness. The last 5.8 miles or so are along an old road which eventually turns into a drivable road. A 4-wd vehicle allows you to drive further in on the road from Harrison Pass and will save you about 3.2 miles. If you don't have a 4-wd in your ferry plans, park the car at or near Harrison Pass.
I took 3 days and 2 nights to hike the trail. I'm in pretty good shape. The 1st day I hiked about 5 miles (2.5 hrs) and camped about 3/4 mile west of Favre Lake just off the trail. A small stream is nearby for water. The 2nd day I hiked to Overland Lake, about 12 miles. Actual hiking time (without breaks) was about 6.5 hrs. The 3rd day I hiked about 16.5 miles and I figured I was walking about 8 hrs. Total walking time was about 17 hrs. You can add your own additional hours for pictures, rest, lunch, water and viewing breaks.
Doing it again, I would plan to get over the 2nd major pass and into the North Furlong drainage or even beyond, the 1st day, just past Wines Peak about 1/2 mile is a flat ridge visible from and not far off the trail. That makes the 2nd day to Overland Lake easier since much of this day is at or above 10,000ft. The 3rd day could again be hiked out to Harrison Pass, could be spent exploring around Overland Lake or could be hiked to McCutcheon Creek and find a campsite there before hiking out the 4th day.
Be somewhat in shape. The trail is often steep, rocky and high elevation. I did not find water to be limiting but felt that good campsites were limiting. I did not explore too far off the trail for flat spots but the wind does howl in the Rubies and I did not want to be exposed on the 10,000ft ridge top. Some flat ridges do occur off the main crest but these would add to travel time, mileage, elevation gradients and the need to carry more water.
Water is available at any of the lakes, the tributary to Favre Creek going up the pas to N. Furlong Creek, or Lake. That's about it until the tributaries of Overland Creek which is about 5 hrs or 10.5 miles away. I filled up at N. Furlong Creek and carried a gallon and had plenty of water. If you camp beyond N. Furlong you will need more for dinner, breakfast and the trail. Fill up again at the lake above Overland Lake - it saves 15 minutes of packing water straight up hill. There is water just over the 10,200ft hill in the North, Middle and South forks or Smith Creek. There is also water in a spring 1/4 mile before McCutcheon Creek, in McCutcheon Creek and a 2 springs 1/2 to 1.5 miles after the wilderness boundary and one near where the drivable road begins. Filter or boil all water for safety. Earlier in the year more snow is present and snow melt is flowing and available for use.
Some early distances are 45 minutes to Lamoille Lake, 90 minutes to Liberty Pass, 3 hrs 15 minutes to N. Furlong Creek, 4 hrs to Wines Peak and about 5 hrs to the ridge which has camp sites, not to far off the trail ( which may be the last decent sites before Overland Lake).
When is the best time to hike? It all depends upon the amount of snow, coolness of spring, and snowbelt. Late July or Mid-August are your best bets.
Many people of all ages hike the short, but in parts, steep trail to the Dollar Lake and Lamoille lake. Friends or family could hike this part with you before the more adventurous go beyond Lamoille Lake or Liberty Pass. (Steve reports very few people were seen on his hikes, especially after Liberty Pass).
Another value of the Lamoille Canyon area and the crest trail itself is the tremendous diversity of plants. It's worth it to hike just a short distance to see the mixture of wildflowers, grasses, tress (yes) and shrubs. Wildlife abounds with animals like Mountain Goats, Mule Deer, and Mountain Lion.