PO Chrono purchased in Jan. 2008 kept perfect time for 6 month, then stopped dead. After return from Bienne (and a loooooong wait there) it has run perfectly again.
Also, forgot to enter in the poll, Seamaster GMT ran for 4 months and likewise stopped dead. Authorized service center in Ill told me the pallet fork failed and repaired it. It ran for two more months and I sold it.