I have said it before, and I’ll say it again. Your mission statement is a living document that changes over time.
Do not cut and paste your mission statement. Rewrite it from scratch. Every time.
Why? As your organization evolves, so should the mission statement. It should get better over time. Look for new words. Make the sentences shorter. Throw in a (very subtle) joke. Find ways to shake everything up.
That is all.