I have owned several Jeeps with the aluminum valve stems and the tire pressure monitoring system. My 2007 Commander and 2008 Liberty both exhibited problems causing the tire pressure monitoring system to display false low pressure warnings which are both annoying and dangerous as it becomes a "Chicken Little" scenario not knowing if it may be real. My 2010 Wrangler also has them but has not shown any signs of malfunction yet.
I have not seen any signs of them splitting nor any overt signs of corrosion upon inspection, but they have been reported to the service department every time the vehicles were brought in for other service and maintenance. Nothing was ever done to alleviate the problems. I am sure I am not alone with these issues.