I notice those bars are not sleeved or bulged at the stem. (No surprise, these are hardly for racing.) That increased outer diameter goes a long ways to reducing the stress at the stem edge. Aluminum handlebars fail with use, faster with hard use. That is simply a given. Better design, execution and alloys will postpone that failure but not stop it. Best approach is to simply replace aluminum parts (especially those that are cantilevers with real force applied like handlebars and cranks) before they break. (And those near pristine bars and cranks hanging up in the garage of that neatness freak who is also an animal on the bike - leave 'em hanging. Don't put 'em on your bike!)