Three numbers — current age, retire age and planning horizon — define the entire timeline of your simulation. They are the most powerful levers in the tool, and the easiest to overlook.
The age you are today. The engine uses this to calculate the length of the pre-retirement accumulation phase.
The age at which drawdown begins. This is not necessarily when you stop working — it is when the portfolio starts being drawn on.
How many years from retirement you want the plan to cover. 30 years from age 60 takes you to 90. Use at least 25 years — most retirement planning underestimates longevity.
From current age to retire age, the engine runs contributions, investment growth, and any expenses configured to start before retirement. Pre-retirement spending is fully supported — each expense has its own Starts setting: Now, At retirement, or a Custom age.
Total months = (retire age − current age + horizon) × 12. Every path runs the full length. Ruin is recorded when both the portfolio and cash buffer hit zero. The cumulative success probability chart shows how the probability evolves across your entire timeline — notice how it steps down at retirement age when drawdown begins, then stabilises.
Each additional year of work adds one year of contributions, one year of portfolio growth, and removes one year of drawdown. The combined effect on success probability is larger than almost any other single change. The portfolio value fan chart shows the spread of outcomes — the pre-retirement phase is the narrow left section, with the fan widening as uncertainty compounds through retirement.
Reducing the horizon from 30 to 20 years will raise success probability, but it means the plan does not test longevity risk. Use a shorter horizon only if you have specific reasons — not to make the numbers look better.