The Wonderland has big daily elevation changes. When I hiked it about six years ago, with more or less traditional gear, my group planned nine days and finished in eight. Since then, I've hiked sections of the Wonderland, with ever decreasing base weight.
Last year, first week of August, I hiked a figure eight loop incorporating part of the Wonderland with BW >8#. Plenty of snow still on the ground. My biggest day, IIRC, was ~17 miles. I felt like I was moving reasonably fast, although I could have hiked longer each day.
Trip report here:
Others here have also posted TR from Wonderland and Rainier NP.
I seem to recall reading something from Ryan Jordan, talking about his 3 day WT attempt.
Five days would be v. tough for typical (ie, traditional) hikers, in my opinion.
Edit: Just found the Ryan Jordan thing--he was actually attempting a 2 day hike, and he _did_ succeed "but couldn't stand to eat another macadamia nut for six years.".