Now that we know how to start a fire, when should we start one. Hopefully not when we are lost and soaking wet and cold.
It's situational, obviously, but what goes into my assessment is:
1) I want at least 30 minutes of prep in gathering fuels and setting up my starting fire structure before ignition, to ensure a successful fire in bad conditions that I can tend 100% without needing to step away while it's still building. It's not the kind of thing you want to start-over on because of a fail.
2) With that 30 mins in mind, how am I or the people I'm with holding up, in the given conditions? Mental toughness is a thing, but a kid, someone out-of-shape, or an inexperienced person will mentally check-out quicker and will start exhibiting shivers, and just quit on the trail earlier. So that needs to be the barometer - what's the condition of the weakest person, not what the toughest in the crew can handle.
3) What's the trend in the weather - what is it most likely to be doing in an hour? What's the worst case for that weather and my/our condition at the moment? If worst case hits in 5 mins, do I have my 30 mins of fire prep time?
4) Location - if I come into a wind-sheltered spot with easy access to fuels, and all of this decision making is on my mind, that might be the trigger to call it a day and build a fire. As opposed to driving on, especially if what's ahead might have less fuel (above a treeline, for example) or be more exposed to the wind.
5) Err on the side of caution - things can go wrong in building a fire, from wet or hard-ignition fuels, to a mistake in trying to put too big of a stick onto a fire-structure that isn't ready for it yet (and killing the flame). And people can be in worse condition than they realize - especially if you're older, male, and have a background that includes a lot of mental toughness and hardening experiences. Things can sneak up quick and viciously on people with that profile, but also on people in general in cold, wet, rugged terrain. Don't take unnecessary chances, especially if not dead-certain of where the truck is and exactly how long it will take to get there.
6) Balance your values of toughness with values of
competence. Competence requires better judgement than toughness. Toughness gets you through some difficult things, and is important, but often equates something like stopping to build a fire as "quitting", instead of being the prudent and wise decision. If you value competence, stopping to build a fire is not a difficult decision - it's a logical one, not an emotional one.