amortization of intangible asset

As per para 68 of AS 26, the life of intangible asset may be long but it is always finite. So, i think you will need to estimate the life.

as per AS 26 useful life of an intangible asset may be very long but it is not infinite. The entity should measure the useful life reliably. 

there is rebuttable assumption that the useful life of an intagible asset <= 10 years. it does not mean that useful life cannot be morethan 10 years. if the entity can prove that the life is morer than 10 years, it can be amortise over its useful life.

if it can not be prove that, amount should me amortise over a maximum period of 10 years only.