It's cloudy, typhoon comes and goes and that's why I remained silent for so long. Glad that you are still here around reading this.
For some amateur astronomers, after several years in the hobby, we might begin to buy and sell. First of all, our observation habits might change, let say from visual to photographic, from deep sky to solar observation, from highly portable to bigger aperture, etc. That would push you to sell and buy something else. Secondly, we might make wrong buying decision, we would also need to sell. Thirdly, when you reached a certain critical investment, you will not pour too much extra money so that you can control yourself, and in that case, you will also need to sell. And there are far more reasons to buy and sell. Therefore, equipment trading seems part of the life of some amateur astronomers. Yes, if you're a regular visitor to astromart or similar website, you will probably agree with me.
Recently with the change of my life style, I did quite a lot of selling and buying. In terms of astronomy, I'm even more "portable" mind now and I spent far more time on solar imaging than anything else. Basically I know what is my cup of tea right now and thus some equipments which I found useful once upon a time, now I found them less valuable to me. Selling them will give me some cash so that I could buy something else.
Equipment trading could be great in another sense. Somehow when you found the need to sell, you will choose between your gears. Which of them are truely useful to you?
A question which pops up from astronomy forums regularly. It's something like which telescope would you settle if you're allowed to own only one of them? Which single (or up to three) eyepiece you would keep if you're allowed to keep a certain number of them only?
You will not be able to answer these questions in a very real manner unless you're going to do that in real life!