Ask HN: What's the average amount of time for a startup to break even?

1. After how much time does a start-up usually break even or become profitable?

2. If they aren't break even for too long, does that mean that their product just isn't adequate for the market?

3. After how much time being unprofitable do investors just decide that this company is not worth any more investments?

I would really appreciate to know these answers (or assumptions, experiences), since it would give me a better understanding of the probabilities of success for some start-ups I've been following.

Thanks!