Amortisation of website domain - capital allowances

Client has purchased a domain name for 10k this year. I appreciate this should be treated as an intangible asset (much as I'd prefer to fully w/o now) and therefore they can claim either 4% or the amount amortised in the accounts. My question is how would you judge the economic life of the domain? Has anyone had experience of this before?

I appreciate that was two questions.

Nigel