Haven't gotten my nerve up to see how long he'll stand
I hear ya on that one.
I never tempted fate with ground tying. I would say a stern "WHOA!" before I left, then kept her in eyesight when I entered the open barn to get whatever I needed while she stood on the driveway with the lead rope dangling to the ground.
I have instilled the fear of God into my horses so as long as I kept her in eye contact if she did move a hoof I could bark out her name and she would snap to attention. (Which has come in handy so many times when they are doing something you don't want them to do.)
I always marveled at the old Westerns, how they would drop one rein to the ground and walk away with their horse in park, but I was never that brave. I used ground tying for situations like bathing, clipping, grooming or etc. when I was right there with my horse and *could* grab the leadrope if it was necessary.