Valid to date - task list

Dear ABAP gurus,

Iam using change number to create Inspection plan. System is displaying always Valid to date as "31.12.9999". But as per business requirement of the client, validity period is 3 yrs. How can i change the date.

1) Can i cahnge at change number level?

2) or At inspection plan level?

Iam giving you the details of the field at Inspection plan level.

Transaction: Qp01

screen no: 1200

screen Field name: PLKOD-DATUB

Program name: SAPLCPDI

Package: CP

Pls guide me how to get "valid to date" as 3 yrs plus "valid from date".

thanks and regards

Venkat. V