Depends on your level of fitness and how fast you hike. I've hiked the entire trail in a day but that involved leaving early, hiking at a good pace and staying out until dinner. Leaving from Mew lake makes it a little shorter.

Keep in mind the lookout on the 2nd loop of the map on the way south is no longer much of a lookout, the trees have grown up and blocked much of the view.

I did this trail October 2016. I stayed at Faya for 2 nights and explored during the days. I did both lookouts in one day, but I only had my camera equipment with me so it was relatively easy to hit up both. I will say that the lookout between Faya and Head Lake is not that great. As mentioned already, the trees have grown and block most of the view.

The Starling Lake lookout however is fantastic. I highly recommend checking it out. 

Its nice. You'll notice it because the rest of the time you're staring at trees but you won't be startled.