Dear Shree,
Changing the useful life of the asset does not change the depreciation amount posted so far. It will adjust the revised depreciation amount in the coming period. Since you have already done the year end closing for 2014, it means the books are depreciation is posted till Dec'14 in both the books. Now if you change the useful life of the asset, the revised depreciation will be calculated and your depreciation amount from period January will be changed.
The change of useful life does not affect the posting already made. so I believe it will not affect your asset closing for March.
Please let me know in case of any questions
Regards,
Sumti Bhadani