However, Cloudflare has 79.2% gross margin, indicating that delivering their services is highly profitable. If they ever needed more money, they could simply raise it or scale-back in other areas.
TLDR: They could go for a very long time.
That's incorrect. They didn't burn $77m in cash in the quarter, GAAP net loss is not equal to them losing cash from operations. The calculation doesn't lead out to six years accordingly. They're no longer burning cash (as they previously were):
"Net cash flow from operating activities was $40.6 million, compared to negative $8.8 million for the fourth quarter of 2020. Free cash flow was $8.6 million, or 4% of total revenue, compared to negative $23.5 million, or 19% of total revenue, in the fourth quarter of 2020."
That could still slip back occasionally into the red, of course. More likely it's going to be two steps forward and one step back, culminating soon in predictably cash flow positive operations.