One day through hike in uppper enchantment is doable (we did it in July), but you need to bring a headlamp in case you come out of the dark. IT is a gruelling 19 miles hike but the view is top notch. Upper Enchantment is HIGHLY recommended especially in fall, lark tree will turn yellow and shed beautiful colors on the lakes.
If you can only do part of it, I recommend Lake Colchuck/Lake Sturat side. Snow Lakes side of the hike is long and boring. Hope this helps. Enjoy!