A fast sustainability check for a single pot of money. Enter what you'll have when you stop earning, the return you expect it to make, and how much you'll draw. Plumb Line shows whether it lasts, grows, or runs aground, and in which year. No accounts, no imports; just the question, answered.
Deterministic monthly-compounded drawdown: it compounds a steady average return and excludes volatility and sequence-of-returns risk (a poor run of early years depletes a pot faster than a smooth average suggests). A "sustains" verdict means it passes the first test on average, not that it's guaranteed. For thinking, not a forecast.