How long does a Will last? Is it "valid for life"?

Technically speaking, provided your Will is legally valid to begin with, it lasts till you revoke it, or you get married (in which case it gets automatically revoked). It remains valid through divorce though. So it possible for it to be "valid for life".

Regardless, the better question here is how sure are you that your intentions will not change over time? We understand that due to the current Will writing system out there, the high costs of writing Wills is deterring people from re-looking at their Will and wanting it to be a one-off event.

Think of a Will as a plan for your kids and your stuff post-mortem. Your circumstances do change over time and so should your plan be updated accordingly. Since a Will is arguably one of the most important document in a person’s life, it should be drafted and considered carefully, and be re-looked at periodically.