It’s absolutely sustainable if your lack of profit is being made correctly. If Amazon ever decided to stop growing they’d make a ton of profit. But they aren’t doing that, they reinvest, often times into very expensive ventures, which makes them “profitless” in the big picture.
They don’t really lose money year after year, they spend themselves back to zero year after year. That’s very sustainable.
Then you definitely should invest your money with them, if you’re not already.
I choose a different direction for myself though.