Self-belay kit YES, because if you don't have it on a climbing path and a rock hits you it can end the worst, a couple of 100 meters lower, in case of self-belaying, if something hits you, severe pain, the kit saves you from a worse fall, with the self-belay kit that has a box unfortunately after a fall the usage period expires, not safe anymore, but if they said that, no one would buy such a kit, I used it only 1x on Via della Vita, elsewhere I trusted my hands, carefulness, observing, attentive to what's happening higher up, but this doesn't help much when it flies, flies like a bolt from the blue....but you need to know there are also many climbing paths without protection for self-belaying, mandatory use of hands for progressing...alpinists use ropes and various technical aids for safety, in case of a fall it ends well, we hikers take these damn paths too lightly, wet ground, mud, rock, good combo to fall into an abyss. Life is only one, my opinion.