Having been around since 2003 and never once taking a hiatus, I've participated in every event and read all of the manga (I think?). Though there are always times when I don't catch on to a reference. Fremere & Reiko, for example. I have no idea what they are about!
My complete involvement in an event or manga update is definitely choosy, and I often end up just skimming if I'm not entirely interested in the plot. Sometimes I don't even try to earn all of the items in an event if I don't like them or I find the actual event dull.
So I guess I'm a bit of both. I've followed everything serially throughout the years, but because I've often skimmed through plots, I have gone back to reread things if I'm really curious about what's going on. With all of the new items being released, it gets harder to keep up.
And seriously, who are Fremere & Reiko? emotion_facepalm
Fremere's Guard, an Item, and Reiko is a character from another item, called Anima Adamantea.