I mix both techniques of habit, I can write in my lunch hour and get a good forty minutes in but then if I have ten minutes before work in the morning it's incredible how those sprints stack up. It's the same theory as those bank accounts that round up spends by diverting the difference into a savings account.
The advantage of it is that you get a good stack of words over a period of weeks without feeling too much pain.
The key to success at this is planning. The one downfall of short spurt writing is having to spend an age remembering where you're up to. I write out the plan of what I'm working on as a series of story tasks. Things I have to get across to the audience in order for the story to make sense.
Then I work on the story one task at a time from point A to point B. So when I check in for a five minute burst I am only focused on the next task.
Of course you may lack the time to map out every task in one go. So to combat that I use a technique called splitting. When you split you take a relatively large chunk of story and split it into two smaller chunks. Then you split those chunks into two more down and down until you have a chunk small enough to be a task that will cover a couple of paragraphs.
So if you're not actually writing the novel with your five minutes you can be splitting your plan. You have to have the attitude of a marathon runner to get this done but it will pay off eventually.
EDIT: In response to the comment below I'll go into what I call a story task.
It's a famous trope in writing that you want to give your story dynamism by boiling it down to a single sentence e.g.
"An epic tale of love and betrayal set against the backdrop of the Great War."
From this boiled down hyper synopsis you can make a short list of things that this story should include to be "fit for purpose":
- Must include love
- Must include betrayal
- Must be set during the Great War
So obviously you're going to go off and read a bunch of stuff about the Great War for verisimilitude points. Let's not worry about that. Let's worry about love.
So if you think generally about love stories they all describe how, as Shakespeare put it, "the path of true love never did run smooth".
You know you will have at least two characters, they are going to be the two people who fall in love so we get a whole new implied list of things we already know about our story from this.
- Will detail a troubled love affair
- Will have two characters who fall in love
So let's split it down further. Let's take just one of our two lovers. Let's call him Daniel. We already know some stuff about Daniel just from our set up.
- Is a romantic
- Lived during the Great War
Because of the latter we could probably take the path of least resistance and make him a soldier. So many were.
- Is a soldier
- Was twenty two at the outbreak of war
I made up the second one because I figured mid-twenties would be a good age for a soldier and half of a love pair during the great war. This means he was born in 1892. I'm British so, following the path of least resistance again, I'll make him British too. Now we have some more story decisions to make.
This story I'm imagining has the implication of epic, from the Great War setting, but how much grit do I want it to have? Well, I don't want it to be totally fluffy, I may as well shift the setting then, but I also don't want the trench foot and starvation to detract from the melodrama. So we can think of a few things that it would be helpful for Daniel to be to make the magic happen.
- Daniel is reasonably well off.
- Daniel is intelligent enough and wealthy enough to be an officer.
Being rich, particularly in a time of war risks making him unlikeable so let's make him super nice:
- Daniel is courageous, generous and kind, he cares deeply about the men in his charge.
We can keep riffing like this back and forth in the interplay between the reality we are trying to portray and the functions the various parts of the story have to perform for the audience to both buy it and like it.
It's not very romantic, from a creative perspective, but our characters, settings etc. are our tools. If we craft them wrong then the story won't behave. We might know that Daniel is kind and brave but we have to communicate that for the story to work.
So we come to two story tasks:
- Task One: Establish that Daniel is kind.
- Task Two: Establish that Daniel is brave.
We also have tasks left over from the big story:
- Task Three: Describe Daniel's first meeting with Joanna (I just made up that the woman he falls in love with is called Joanna.)
And so on.
As you can see, breaking the story down into things that need to be there and then turning those necessities into tasks is a process that can be done in the odd five minutes here and there. Eventually you will end up with a massive list of tasks. Then any short writing stint is just a matter of crafting the next task into prose and the business of writing is just slogging through the list.
It's a first step and it won't produce the finished product whole and unblemished but it will get you between 70-80% along the road to completion. (DISCLAIMER: That last 20-30% though, that's the doozy, edit and polish, edit and polish...)