That critical point could be reaching profitability, or signing a large round of funding, or landing a key client.
Most of the co-founders I've talked with, or have heard speak publicly (I counted at least 2 speakers this year at startup school), borderline brag about how they went x number of years with no salary. I think sometimes it's an act. There's no way declaring bankruptcy or defaulting on your loans can feel good. Other times I feel like that's a direct influence from investors. For example I've heard verbatim the following sentence from an investor:
"We want you [speaking to an audience about investing] to live like college kids. You know, eat ramen noodles, borrow food from friends, live on your buddies couch, take the bus to the office. At no point should you rely on investor money to pay your own bills"
A part of me agrees with that mentality. You should be financially independent of investor money as a co-founder. Another part of me sees a benefit in keeping a co-founder at some level of comfort. If they don't have to worry about paying for food this month then their work performance would surely increase.
