Whoa!!! First time I've every seen one completely snap! Seen a few bent but rare. A couple of years use? not bad at all ....Can't say that about much else on these machines!
Sizing up to a 1/2 x1/2 most likely will reduce the chance of ever snapping a shaft again.
Keep in mind they are a wear item. Their cheap enough to replace on a regular basis as a part of maintenance. I'll go through mine periodically replacing ones that are loose or show signs of galling and binding.
I'm using the rubber heim boots on my next set. The protection the boots give plus filling the boot with lithium grease, as a lubricant and a extra barrier against water and dirt should dramatically extend the life span
I use these folks for all my heims and related stuff. Great company to do business with.
http://stores.ebay.com/QS-Components...p2047675.l2563
The boots-
http://www.ebay.com/itm/Seals-it-Rod...item4ab9719b4e