handlebar as a maintenance item and recommend that it be replaced at least every two years.

They flex and twist, and so are a fatigue item. Adding bar ends adds leverage, and thus more evil, flexy twisty-badness.

7000 series alloys are only good for elongation or stretch of between 3 to 9% before they fail. Depending on the alloy. The aircraft I fly has a 7075 alloy spaceframe. Just taping my GPS on it has the maint-crew screaming hysterically.

Bar ends are thus the Work of Satan, especially on aircraft, Mezzos, and other fine pieces of engineering. They'd be OK on a Brompton. Strike that from the records.

Seatposts, in my slender MTB experience, tend to break before handlebars because they have more load, and more torsion. They are often made of 6061-T6 alloy or similar, which is good for about 25-30% stretch before fracture. Many road bars are made from 6000 series alloys because of this. A lot of bikes though, still use 7050, or similar, especially in alloy stems.