You can't teach an old dog new tricks.

Who is too old to learn is too old to teach

That would be an old dog learning new tricks. This is not a company or a management team that has been willing to admit they are making mistakes.

If the old dog barks, he gives counsel

We pulled it out of our old bag of tricks.

I'm 39 years old, but in dog years I'm really 55 or 60,