How to change the Life Months of an Asset Master?

I am attempting to change the life months of  an existing Fixed Asset Master and have been able to find documentation with instructions. When attempting to update the life months in the depreciation defaults of the asset (P1202), I receive an error message: Invalid User Defined Depreciation Rule. Are you required to setup a depreciation rule for every combination of method/life months that may be used? The documentation seems to imply that the life months can be changed in depreciation defaults for the asset with no further modification to depreciation rules.

THank you.