The risk and return components of the efficient frontier are computed for a specific time period, usually one year.

FORBES: The Efficient Frontier

We had one holiday a year usually by the sea for a week, Dad hired a car and we stayed in a caravan.

BBC: How much do families spend?

Guildford Borough Council said that new tenants would be given a one-year introductory tenancy followed by fixed term contracts usually for five years.

BBC: No more Guildford council lifetime home tenancies