There have been some known issues on this since both devices cannot agree on a real time to create the rekey, what I mean is that Cisco Gear might want to do the rekey after 90% of the lifetime might have passed and proably this 3rd party vendor will do it later or sooner. But the truth is that you would need to run some ike and ipsec debugs to see why this tunnel is not kept after rekey is complete.
