dang, that's extreme! I'd say avoid any more 3TTTs since they are proving unreliable. I wonder if you have the proper diameter bar in there (are you making a 26.4 stem clamp a 26.0 bar?) Otherwise I've never had a Cinelli break yet, or strip out (always grease the threads) but have had it happen to some French stems and cheepo Italian stems. If you can stand modern stems the Cinelli "Frog" seems to be popular and the detachable plate might prove stronger and less likely to strip...but I don't have first-hand experience with it.
edit: plus if you are really concerned with stripped threads something like the Frog can allow you to shoot in Helicoils to replace the aluminum threads with stainless steel, a trick that has saved countless VW engines from the scrap heap. Unfortunately you can't shoot Helicoils into a typical road stem, I've tried.