Campaigners have criticised delays to the project to restore the historic winding towers at the Cefn Coed Colliery Museum near Neath.
The Welsh Government, which owns the site, began to dismantle the listed structures on safety grounds in November/December 2016.
In May that year, Neath Port Talbot Council granted planning permission for the project, on the condition that the towers were reinstated within two and three years respectively.
With the deadline for re-erecting the first headframe rapidly approaching, the Welsh Government now admits that the project is years behind schedule, with no works contractor in place, and projected costs rising to £1.3 million.
The headframes date from the 1920s, and were in operation until Cefn Coed Colliery's closure in 1968.
One of the shafts continued in use until 1990 to ventilate and access the nearby Blaenant Colliery.
Despite surveys of the headframes in 2013 and 2015, the Welsh Government says further examination of the structures after dismantling revealed more problems.
The Welsh Government has now formally applied to Neath Port Talbot Council to extend the amount of time it has to carry out the work.
The completion dates for reinstating the headframes are now set for mid-2020 and 2021.
The Welsh Government told ITV Wales a number of firms have tendered for the contract to carry out the work, and that it expects to make a decision in November.
Campaigners still worry they'll have a long wait before the headframes tower over the valley again.