I should preface this by saying that I have been using a harness for decades while hunting, but I never used to "tie off" until actually in the stand. Three years ago, after reading some posts about all the falls that happen while ascending and descending, I decided to be more careful (stay tethered) while actually climbing.
Two seasons ago I was hunting from my Lone Wolf. I was using screw in steps, and was up a large straight Ash tree about 24 feet. At the end of the hunt in the dark, I was coming down the tree, removing tree steps as I went like I always do. After removing two steps, all of a sudden I heard a snap, and I was falling. It was as if I was standing on a branch that broke suddenly. But I was standing on my screw in tree steps. I fell about six feet when my harness rope caught me, slamming me into the tree. I missed falling through other tree steps below me (ie. guthooks) because I put them wide enough apart, apparently, and fell between them. The whole thing happened lightning fast, and before I knew it I was hanging there. Don't think that you'll ever have time to react when things go wrong. You just won't. The only thing you can do is prepare for the worst before it happens.
I was baffled, figuring I mistakenly stepped on a branch in the dark and not on my step. Turns out one of the steps actually broke. I have been using the same steps for close to twenty years. Time to get new ones. They fatigue like any material. Imagine bending a tree step over and over hundreds or thousands of times under your weight.
Just before this happened, my brother was coming down the hill toward me and said he saw my red head light just drop, but then it stopped. Glad I decided to tether myself while climbing. I hope you guys do too.