Sub Assets with remaining life

HI Experts,

My client had a requirement of Assets to be split into sub assets with their balances & depreciation.

For that we are going to create sub assets & will transfer balance using ABUMN.

Client is ready with Excel sheet of new sub assets which have their last date (Date till which to be depreciated)  -   what will be best approach for last date of sub assets (or for remaining life)?

I have one solution for it is to update its expired useful life ( Ex. UL = Useful life – remaining life )

But not sure whether it is correct or not. & Expired UL field is not available for sub assets, kindly let me know which check box to be selected in AO21 for that.