As many hikers mentioned it before, I would advise to split this hike in two, the first part from the half moon pass trailhead into East Cross creek campsite and then hike the next day from the campsite into Holy Cross.
We decided to go for the full day hike and it was very demanding to say the least. A solid 8.30 hours hike and we are VERY fit. the way back up into half moon pass after a good 6 hours hiking up the mountain was grueling. beautiful views from the summit though, well worth the pain if you know what you are getting into.