Sadly, I'm one of those cast members. I used to love pin trading. But now I don't. The reason is that some guests who trade pins are CRAZY. Its not fun anymore. We aren't required to pin trade. Its because we enjoy it. But now its not any fun, so the only cast members who pin trade anymore are new hires or ones who pin trade a lot outside of work.
Personally, I stopped pin trading because of one specific moment. I always keep a "mystery pin" on my lanyard. Its always my best pin, to reward people for taking a chance. Well, one guest came up and asked to see what it was. I told him it was a mystery pin, thats the whole fun of it. He then said he wanted to see it, other cast members have shown him theirs, etc. I told him I would answer questions about it, but I cant show him. After all, if I showed him, whats the point of the mystery?
Well, he was not happy with that answer. He started demanding I show him, shouting at me. At this point, I probably should have just showed him and got it over with. But I was just so shocked, and he was making a scene, I just kinda apologized but stood my ground. He stormed out of the room, extremely pissed off. I went about my shift, kinda annoyed that he made such a scene over a dumb pin.
Then his wife came back in the room, slamming a pin down on my counter. She then loudly and rudely said to me, "This is my worst pin. Now give me your mystery pin." I calmly handed it to her, still giving her my trivia about it and why it was the mystery pin (it said 1928 on it, which is the year the area of the park i was in was modeled after). Without another word, she stomped out of the room. I then went right into my lead office, removed the lanyard, and told my lead I was done pin trading as a cast member.
That kind of thing happens all the time. Guests get so wrapped up in getting all the pins they want, they ruin all the fun of it. They just stomp all over the cast members like we're trash. Its just degrading and not fun at all. So whenever you see a cast member without a lanyard (most of us), it means they have had an experience similar to mine and become just a bit more jaded than before.
To answer your last question there, pins are refreshed in the morning, and only later in the day if we have any. As of the 60th, we've been refreshing when possible, but its the lowest priority thing on our to do list. We usually just put good pins on in the morning, and refresh maybe once later if we get a bunch of pins so lame no one will trade anymore.
Oh but, thats pin board trading only. If its a cast lanyard, they can refresh whenever they feel like it. We have to be sparing, though, because we don't really get a lot of refresher pins in most locations.