How to reduce Asset useful Life for running asset & Minimize Scrap Value

Hello Experts,

                  We have the following requirement. The scenario are explained below.

There are more than 2 million assets running for more than 8 years whose useful life is 15 years & scrap (Residual ) Value is 10 % of acquisition value.

Now the requirement is that to reduce the useful life to 12 years & maintaining scrap(Residual) Value to 5 % of acquisition value

Kindly advice

Best Regards

Ashutosh Saraf