In my current writing piece, there are two main characters who are in two very different (and far away) settings. During the story, it goes back and forth between the two. The problem is, one of the main characters is a soldier and the time period is much longer for him than the other character, who lives in an urban environment. While it may only require several pages to describe a week-long trek by the soldier, the urban dweller is involved in many events that take a short period of time. Describing a week in her shoes could take several chapters. Any ideas how to solve this problem, if it even is one? I have, in my opinion, good chapters for both of the characters, but I can't seem to link them in one coherent time-frame. The soldier's story takes place over several years, while the other main character only as a year of her life written down. I'm at a loss.
Can you space out her events? Things might not have to follow quite so fast after one another - she can have down time too, or at least spend weeks at a time busy with things that are important to her but not to the plot that you can summarise in a few words. And maybe try to slim down his story as well? It wouldn't be too bad to tell them out of time with one another as long as you still had links back. If the 2 stories are so disconnected then you might as well write each as a separate novel, with her story just happening to take place around the same time as one of his things. Or JUST tell what he is doing in her busy year, and just find ways of adding more action for him - subplots and stuff. Things to occupy page space as he's marching.
During the middle-ish part of the story, the characters meet and help each other complete their goals (which turn out to be the same). To understand both characters, it's essential that their stories be told at the same time. That's a good idea. I could add in a chapter where she goes into hiding (it would fit well in the story) that could make her time-frame equal the other character. It's not that his story so thick, but the things he does simply take a much longer time. There is actually more information packed into the other character's story, but it happens in a condensed period of time.
I don't think there's a formulaic solution to how often you should change your POVs...it really depends on what the story calls for. The most important part of a story is how good the writing is.
I meant slim down his story time-wise... He doesn't *have* to take that long to do everything. I know exactly what you're going through... I wrote 40,000 words of a draft then decided I had to change the time line, so I'm compressing what was a character's month worth of scenes into 2 days. it's given me a few headaches, but I've managed it without losing anything - in fact, I've added more scenes than there originally were. It feels impossible when you first look at it, but if you take stock of what you've got and try and make her story longer and his shorter (in time) then you can work your way to a middle ground. But it is possible to compress events, more than you'd ever think first looking at a story.
Well, I wouldn't say essential. It's very possible to have a strong secondary character come into a novel later than most, only to have a huge impact on the main character. Said secondary character can have their previous story explained through dialogue, monologue, or flashback. But, in the interest of your story, it depends on what works. There's two problems you'll face with multiple characters. The first is that your readers may only like or relate to one of them; if that character isn't in the story enough, the reader may not appreciate it as much. The second is that with two main characters, you have a hell of a workload before you to make sure that they're both successful protagonists, even if they're not successful at what they're trying to accomplish. You can however, do some creative things with two protagonists. A book I recently read that employed such technique was Snow Crash. The male protagonist's (named Protagonist, it's amazing) usual exposition dealt with explaining the world and its current state, including what lead up to such changes and their cultural effects. The female protagonist's (nicknamed Yours Truly) standard exposition detailed how most people view the world on a subjective level, as well as how the environment has affected the people. Such a thing wouldn't be possible with only one protagonist, but this technique gives each character a nice little quirk that separates them and keeps the story new and fresh and interesting.