On some years, the wildflowers can be good from North Lake and over Piute Pass. You can get halfway down the canyon in the first day. Then, down to the bridge and back up toward Evolution may take you the second day. From there, getting up to Darwin Bench or to Darwin Lakes should be an easy third day. On some years, the flowers at Darwin Bench are very good. Then, you might be able to get up over the Col and all the way down in a fourth day. If you haven't been up to high elevation lately, then the 13,000-foot thin air will kick your butt, so it wouldn't be stupid to allocate an extra day.