I saw a production of the play Driving Miss Daisy today that taught me a new lesson in plot. Typically, specific events are the basis of plot. In the case of this play, the plot was fueled by character development and time progression instead.
Character development is important. It is essential to almost every story above a few thousand words. When a character changes, the flavor of the story changes. It might not be a change from chocolate to vanilla, if you will bear my analogy, but rather french vanilla to regular vanilla. If a story stays the same flavor for too long, readers are likely to check out. Tweak the flavor of the story enough and you can actually create movement of story. You can achieve plot with character development. Some short stories have exclusively character development fueled plots, to varying levels of success. It's very difficult for a story to have what I would consider an excellent plot without any sort of traditional plotting, unless character development is combined with time progression.
I read a lot of stories that take place over very short periods of time. Many quick, unique events earn the limelight for a few pages, each of which move the story forward just a little bit. This is a very common form of traditional plotting. It works. When you tell a story that takes place over a long period of time, however, the events tend to take the back seat. There are important plot elements sprinkled here and there, but many scenes don't matter much in the grand scheme of things, from a traditional plot perspective. If characters develop over the course of a bunch of these unremarkable scenes, what you get is a different sort of plot. You get the sense of progression that the concept of plot really boils down to without much plot in the traditional way.
Using time progression and character development in tandem does not sound easy to me. I like stories that take place over months, not decades. I'm not opposed to the Driving Miss Daisy type of plot though. If you can make it work as well as it did in the play, then you have nothing to worry about.