I undertsnad some people start someday, add a few parts later on, then continue, then leave it aside for a month or two, do something else, and come back with a fresh mind about it, add, leave, etc

While some concentrate on one song non-stop.
Wich way produces the best resuslts in your oppinion.
And if you add it all up, how much time do you spend working on a single track including composing, aranging, 'bug-fixing', and finalyzing your work. How much time do you put into each?