Change useful life of an asset class - change asset class?

Hi all,

My customer has an asset class that now has useful life 20 years but they want to change it to 5 years. I know that it is possible to change depreciation key to LINR and then change the useful life. It is also possible to create a new asset class and transfer this assets to the new asset class with ABUMN. It is 170 assets in the asset class, is it better to change asset class to a new with useful life 5 years?

If I change asset class how will the depreciation when I do the first depreciation in the new asset class?

What is best for my customer?

Best regards Lisa