The phrase "are to prolong" is correct and usable in written English.
It can be used to indicate an intention or plan to extend something, often in a formal or structured context.
Example: "The measures we are to prolong will ensure the sustainability of our resources for future generations."
Alternatives: "are meant to extend" or "are intended to lengthen".
Shorn of their youthful attributes by the march of time, ageing athletes must look elsewhere to maintain an upper hand over opponents if they are to prolong their careers.
Ashley Cole broke down in tears as he, Frank Lampard and John Terry saluted the arena during the Chelsea players' end-of-season lap of appreciation, and José Mourinho confirmed the club intend to take stock over the next few weeks before determining whether the experienced trio are to prolong their careers at Stamford Bridge.
Trapattoni faces the daunting task of having to take something from reigning World and European champions Spain in Gdansk on Thursday evening if his side are to prolong their interest in the tournament after a morale-sapping 3-1 defeat by Croatia in their Group C opener last night.
In advanced breast cancer, the primary goals of treatment are to prolong and improve quality of life (QL) because the disease is generally incurable.
At present, metastatic breast cancer is incurable, and the main goals of treatment are to prolong life and reduce symptoms to maintain quality of life.
Considering the high efficacy of taxanes in breast cancer, new antimicrotubule agents including eribulin are expected to achieve the primary goals of systemic therapy, which are to prolong survival and improve quality of life, thereby realizing the wish of patients with an incurable disease to live longer and better.
To admit insomnia is to prolong insomnia.
The goal, I said, was to "prolong your life" as much as possible.
One way of postponing the issue is to prolong your studies.
Next month, the government must seek a new mandate from the Bundestag if it is to prolong its mission in Afghanistan.
But the impact of those discoveries on the world's mightiest dictatorship may be to prolong its reign.
