Revised lower life cycles of certain rotating parts of the CFE738 engines on the Falcon 2000 prompted a proposed AD to require replacement of these parts before they reach the new reduced limits. Specifically, the HPT stage 1 aft cooling plates would have to be replaced on or before reaching 3,500 cycles since new (CSN). The HPT stage 2 disks would have to be replaced on or before reaching 2,700 CSN. Parts and labor combined are expected to cost about $59,000 per engine. The FAA reported no part failures to date.