As a knitter, I find that if I put a piece of work to one side – sometimes for months on end – the tension is noticeably different when I start again.
I have the same concern regarding a protracted piece of writing. I have been working on my novel for over five years, but with many interruptions. Life has got in the way repeatedly – via work commitments and family health issues – and I now fear my manuscript reads more like a series of short stories. One of the major reasons I have not been able to make any real progress for the last year, is that I have been involved in running a family business. This has given me an idea for an entirely different story.