DNS Authoritative server lease lifetimes
Tim Wattenberg and I recently published a new internet-draft: DNS TIMEOUT Resource Record that provides a mechanism for authoritative DNS servers to save a lifetime for other resource records in the same zone.
Lifetimes are sometimes associated with records based on the source of the record. DHCP based address assignments have a lease lifetime as well as DHCPv6 prefix delegation. Service Discovery DNS UPDATE registrations use an EDNS(0) Lease Lifetime Option to attach a lifetime to the services being registered.
If you have other uses for TIMEOUT resource records, let me know!