Does some degree of stubbornness help for a researcher? Doing research requires exploring a tree of different ideas and then, upon failures, tracking back to some extent, up to giving up on the whole project and changing topics (or even quitting your PhD). You might err on both sides: change approach too much, give up too early, or too late. (See for instance this answer or Half good and some not good results in a research paper?). Most importantly, though, often you won't know that you'll actually succeed until you did, and things might look bleak until then.

Does some degree of stubbornness help being a researcher (I couldn't extract an answer so easily from 2)? Lacking that, do you know any metaheuristics to approach this decision?

EDIT: I read this idea off the mention of "stubbornness and self-delusion" in this rant - and I've observed this trait in at least some researchers.

EDIT 2: an answer suggested that I talk about persistence instead. And probably that's the right compromise and what you actually should have. But I prefer the more provocative phrasing, also because I've anecdotical experiences of stubbornness as a "professional risk" of the profession.
Although I understand what you are getting at, I would like to say that stubbornness is perhaps not a good trait for a scientist. My dictionary provides the following: Stubborn: Having or showing dogged determination not to change one's attitude or position on something, esp. in spite of good arguments or reasons.

Clearly a scientist needs doggedness and stamina to endure long and hard experiments, field work, often monotonous work on data and theory, as well as other issues met in the workplace. To be able to change footing in light of new evidence is, however, an important trait. So being stubborn, in the sense of the definition, would be very counter productive in our effort to have science progress. Persistence and perseverance are perhaps synonyms that better reflect the traits you aim for.

So, yes it is important to be able to endure. Being a scientist is usually based on a deep appreciation for the subject and the research, which is why it is possible to endure the pressures that exist. It is a bit like being a top athlete, very few will excel without a deep love for what they do. As soon as you lose the drive it is difficult to continue because of the demands. Maintaining the drive is therefore a very important aspect of academia and the workplace in which you act.