Which type of estate has no specific intervals for renewal?

An estate at will is a type of leasehold estate that can be terminated at any time by either the landlord or the tenant without a specific period or interval for renewal. This means that the tenant occupies the property with the landlord's permission, but there is no formal lease agreement specifying a duration or regular renewal dates. The arrangement can be continued as long as both parties agree, but it allows for flexibility and can be ended spontaneously.

This characteristic distinguishes it from other types of estates: the estate for years has a fixed duration set in advance, the estate from period to period has specific intervals (such as monthly or yearly), and the estate at sufferance refers to a tenant who remains in the property after the lease has expired without the landlord's consent. Therefore, the nature of an estate at will makes it unique in its lack of defined intervals, which is why it is the correct answer in this context.