Personally, although I love playing certain characters, or even returning to them at a later date, I do prefer a contained arc/direction for the character's cycle and life.
I should note, though, that I've been playing the same character, a litorian runechild oathsworn named Rathe, since Arcana Unearthed released up to and through a conversion to Arcana Evolved.
Not only has it been an enjoyable experience, with the character being a lot different than any character I've played, but I can't wait to see how his story plays out.
But, I eventually had to add a second character to the game, not only due to our gaming group having shrunk due to life-change attrition (mostly work, including a player moving to become a professor at DePaul University), but also due to my need to have a change, of sorts.
Fortunately, though, I didn't kill Rathe off in order to play Zhod (Warforged nay-sprite nay-faen greenbond - Seriously long story) and I've enjoyed both characters.
That said, I really think, for me, either campaign breaks, or encapsulated adventure arcs, are a dang good idea when it comes to gaming.
However, it might just be a by product of my life, as I moved around a lot, thusly changing gaming groups a lot, with my current group being the longest gaming group I've ever had, at ~8 years. Before that it was ~6 years (twice), with no other group prior to that going more than ~3 or 4 years due to moving around a lot.
I enjoy the defined arc as it gives you a goal for the story (beginning, middle, and end), while also keeps you from wishing to play something else.
I enjoy fantasy, but I need breaks from it at times, which I use to get when I had two or three gaming groups, compared to my singular gaming group that I'm in now.
Fortunately, we've got a fine DM who keeps things feeling fresh, solid companions to game with, and the outlet of Play-by-Post games on here.
