perpetuity -
An annuity in which the periodic payments begin on a fixed date and continue indefinitely.
Wikipedia
A perpetuity is an annuity that has no definite end, or a stream of cash payments that continues forever. There are few actual perpetuities in existence (the United Kingdom government has issued them in the past; these are known and still trade as consols). A number of types of investments are effectively perpetuities, such as real estate and preferred stock, and techniques for valuing a perpetuity can be applied to establish price.