Lacking youthful vigor or spirit; behaving in a dull, listless, or overly serious way that lacks energy and enthusiasm.
acting with an air of seniority
To be arrogant or self-important by acting like a veteran or relying on one's seniority; exhibiting an air of over-sophistication or pride in one's experience despite one's actual age.
vigorously gnarled
Originally describing the majestic and powerful appearance of old trees; used to describe a person with great and heroic spirit