Guernsey's landfill provision should last until 2021, two years longer than previously estimated, the Public Services Department has said.
It said the new estimate was due to the amount of rubbish being dumped halving in the past 10 years.
The department said the level of waste entering Mont Cuet remained similar to 2009 and if this was maintained the site would remain in operation longer.
Deputy Minister Scott Ogier said it was a result of campaigns to reduce waste.
He said: "Through the commitment to recycling and the range of schemes and facilities now available we continue to make good progress, which is in line with our goal of reducing the amount of waste going to Mont Cuet. Islanders are doing a great job."