The coal evolution is in stage of maturity to over-maturity.

煤演化程度处于成熟—过成熟阶段。

youdao

As the Speak Mandarin Campaign enters its 20th year, it has now reached a stage of maturity.

讲华语运动如今踏入第20个年头，已达到成熟期。

youdao

After a while, people became attached to a certain brand and at this time sales leveled off (stage of maturity).

过一段时期，人们变得倾向于某一种牌子并且与此同时价格趋于平稳(产品成熟期)。

youdao

You might just fulfill them with slightly different products based on the stage of maturity that businesses are running.

WSJ: Managing in Asia: Dell Goes Local; Steve Felice

He insisted that the U.S. had entered a stage of maturity wherein a 1% to 2% annual GDP growth was all that could be maintained.

FORBES: Digital Rules

Trying to build a new core consumer at this stage of business maturity may prove to be fatal.

FORBES: JC Penney's Misfire: What Went Wrong