I bought my first metal detector and dug my first Minie ball in 1974, so the answer to your question is, 38 years.
There are two reasons why I "know so much stuff":
First... like you, I wanted to know the CORRECT identification of the stuff I was finding. In particular, I did not want to "cherish" an object as a being a Confederate civil war relic when in actuality it was a 1916 Model-T Ford car part.
Second... when I became a dealer of civil war relics (1976), I wanted to be as certain as possible that the ID-labels I put on what I sold were correct. (I call that "Dealer Integrity.") So, I did a lot of research to make sure.
To do that, I bought a lot of civil war relic reference books (on bullets, buttons, buckles, etc). But just as important as the books, I frequently consulted a couple of "oldtimer" relic experts, who very generously gave me their time and their knowledge. I've never forgotten their generosity (and lengthy patience) with a full-of-questions young digger (me). Nowadays as an oldtimer myself, it's my duty to be the giver of the knowledge. THAT is why I post in the What-Is-It? forum here at TreasureNet. Someday it will be your turn, so keep on learning as much as you can. Contrary to popular belief, there is no such thing as a stupid question.