Just about every writer I know will endorse the philosophy of ‘write every day’. One of the primary reasons is to foster habit (especially among those of us who are holding down full-time jobs — which is most of us); another is to maintain momentum.
I am a momentum writer. Time and again I’ve demonstrated that if I lay the story aside for longer than a week or so, it takes a tremendous amount of energy and time to get back into the zone. Loss of habit is certainly a factor, but in my case it’s more about losing my handle on the emotional level of my characters. Sure, there’s a loss of general train of thought, but I usually know broadly where events are going. Problem is, it’s the characters that need to get me there, and if I’ve lost my grip on them emotionally it’s, well, impossible actually and demands copious reading back over past chapters to reestablish a connection.
So for me writing every day is ten times more effective and efficient than having good weeks and bad weeks. Not only does it mean that I am more productive during the allotted writing periods, but I am able to utilise much smaller and less convenient time-windows. For instance, I am far more likely to commence a writing session after 10pm, or utilise a half-hour slot.
Even better, when my momentum is good and I am writing every day, I am so much happier than when I’m not.