Request Approver is unable to modify Valid To date of roles

Hi Friends,

Request Approver is  unable to modify Valid To date of the roles in the request screen.

However the end user is able to modify the Validity dates of the roles from default 31.12.9999 to any desired date at the time of request submission  but when the request moves to Approval stages(Manager or Role Owner) this date is not modifiable.

I have checked the box "Change Request Date" in Task Settings in MSMP.

Can someone help.

Regards

Mayank