At what age does gyno go away and it's recommended to resort to surgery?

[Cyclone]

I'm currently 19 years old. As far as I know, I started developing noticeable fat on my chest a few months after I turned 18. I can feel the gland under my nipple. 

[Paa_Paw]

Most commonly the condition first appears in early puberty.  In my case, I had it at the age of 12.  
If the condition is going to regress on its own it will usually happen in about two years. 
If the condition has stabilized and been unchanged for two years then you are probably ready to contact a surgeon if that is your wish.  
When the condition appears at other times in life a bit of detective work is involved.  You want to try and figure out what caused it.  There is a very  long list of potential causes.  This is important because the cause should be dealt with prior to having surgery.    

[TigerPaws]

I'm currently 19 years old. As far as I know, I started developing noticeable fat on my chest a few months after I turned 18. I can feel the gland under my nipple.

At 19 you should see an Endocrinologist and have your hormones checked, the best time would be if you could time the blood draw when you feel the pain, itching and when you can feel yourself growing (sometimes you will feel a strange tingling in the gland which again is a sure sign of growth).

Gynecomastia will not go away by its-self, no amount of dieting of exercise will make it go away. Yes you can minimize some of the visible signs due to fat deposits behind the gland which often accompany breast development. But if your breast gland is developing there is little you can do to stop it short of surgery.

Watch your diet, learn about Phytoestrogens they are everywhere and in almost everything you eat, drink and use like soaps; some men are more sensitive than others and they are almost impossible to detect in your system.