Will you lose your trademark if you use it as a noun?

Trademarks that start becoming generic or are converted into customary words, eventually loose protection. If the court declares certain marks to have become customary or common because they have been used as noun by the common public, then the original owner of the trademark would lose its exclusive right.

For e.g.: Escalator was originally a trademark of Otis Elevator Company, but because of its extensive use as a customary word. The company lost its exclusive right over it. Same case happened with the word XEROX.