30 is the traditional age of maturity, according to the bible. Numbers4:3 is often cited and of course Jesus being 30 before he starts his ministry.
I don't care how 'mature' a jw in his early 20s may seem, or how much preaching he has done, you simply have not been through enough sh1t to give practical advice to an adult going through serious problems. At best, you could give someone a pep talk, but anyone can do that. Even if you have had a tough time growing up and had adverse experiences, you need years after that to process and learn from what you have been through, in order to help others.
At that age, you would be embarrassing yourself.