Just how tight does a Blake's Hitch need to be? I keep them pretty snug. It bothers me when the bight that loops beneath the bridge gets stretched out, so I keep it tight and short. I'll even put the stopper knot up against the hitch to prevent the bight from slipping down.
In reading The Tree Climber's Companion, on the subject of redirects, I came across the suggestion that, when untying your climbing line from your saddle while repositioning it, you should "tighten the friction hitch so it doesn't slide."
My hitches could never slide under their own weight, and always require a good firm push to move them. Am I over-tightening my hitches? Just how far down can one allow that bight looping under the bridge on a Blake's Hitch to droop? Is it okay if it slips down enough that the coils turned around the running end start separating? Am I inflicting unnecessary wear on my ropes?