For how long a deferred tax asset created due to depreciation can be carried forward?

there is no specific time limit for deferred tax asset created due to depriciation and it can be carried forward for the useful life of the asset over which the asset is to be depreciated.

Deferred Tax Asset created due to depreciation can be carried forward for unlimited period. Provided asset remain in the use of organisation. 

If the organisation dispose off the asset then the balance will need to be adjusted at the time of disposal in gain or loss of the transaction.