Is twelve months of backtest enough
A year is the default backtest window and the most misread one. The honest answer is that twelve months can prove some things, structurally cannot prove others, and the difference is knowable in advance.
Whether a year is enough depends on what is being asked of it. Twelve months of a high-frequency intraday strategy can contain a thousand trades; the same window on a swing system might hold forty. The unit of evidence is the trade, not the calendar, the statistics in how long to backtest and the sample math in the sample size problem.
What a year can prove
With hundreds of trades, twelve months can establish that the rule set has positive expectancy after realistic costs, characterize the win-rate and profit-factor personality per the WR vs PF data, and surface the typical losing-streak shape. For an intraday system with a defined session, that is genuinely useful evidence.
What it structurally cannot
One year contains one of each season and at most one regime change. A strategy born in a trending year has never met a chop year; the breakdown only arrives live, the decay criteria in when to retire a strategy. And a single historical path says nothing about sequence risk: the same trades in a crueler order produce a deeper drawdown, which is exactly what a trailing floor punishes.
Stretching the year honestly
Resampling is how a year of trades becomes a distribution instead of an anecdote: Monte Carlo reshuffles the sequence thousands of times and reveals the worst stretches the calendar happened not to deal, the method in Monte Carlo for sizing and the comparison against rolling validation in walk-forward vs Monte Carlo. That is why the published figures here pair a 12-month empirical sample with 1,500 resampled paths over a three-year horizon: the year supplies the trade distribution, the resampling supplies the stress.
The rule of thumb
Twelve months is enough to qualify an intraday strategy for paper deployment when the trade count is in the hundreds, the costs are honest, and the sequence risk has been resampled rather than assumed. It is never enough on its own to size against a hard floor, and it is nowhere near enough for a low-frequency swing system, where the calendar must do what the trade count cannot.
FAQ
How many trades does a valid backtest need?
Enough that the win rate and streak profile stabilize, typically several hundred. A year of an intraday system can supply that; a year of a swing system usually cannot, regardless of how clean the curve looks.
Can I trust a one-year backtest for a prop account?
Only after resampling. The single historical sequence understates drawdown risk, and a trailing floor punishes exactly the sequences the calendar did not happen to deal. Monte Carlo over the year's trades is the minimum honest stress.
Why pair a 12-month sample with a 3-year Monte Carlo horizon?
The empirical year supplies a realistic trade distribution including costs; the resampled multi-year horizon reveals streaks and drawdowns beyond what one calendar path contained. Each covers the other's blind spot.
Not financial advice. Performance figures are hypothetical, modeled outputs (12-month sample; ~1,500-path Monte Carlo where noted). Past performance does not guarantee future results. Verify every prop-firm rule with the firm directly.