IAS 16.57 "The useful life of an asset is defined in terms of the asset’s expected utility to the entity. The asset management policy of the entity may involve the disposal of assets after a specified time or after consumption of a specified proportion of the future economic benefits embodied in the asset. Therefore, the useful life of an asset may be shorter than its economic life. The estimation of the useful life of the asset is a matter of judgement based on the experience of the entity with similar assets."
I dont think any period over 50 years would be a foreseeable future.
