What is the purpose of lease obtained?

The purpose of the Lease Obtained is to give you a "Temporary" IP Address that will change when the lease Expired date comes close.

EX: (Lease Obtained: Sunday October 18, 2012 at 12:30:15 PM / Lease Expires: Friday November 12, 2012 at 10:45:55 AM)

"The client starts to renew a lease when half of the lease time has passed. For example, for a 24 hour lease, the client will attempt to renew the lease after 12 hours. The client requests the renewal by sending a DHCPREQUEST message to the server. The renewal request contains the current IP address and configuration information of the client."