What you’ll take away
- Gamma is how fast your risk changes character — and it accelerates violently into expiry.
- Short-dated options pay the best daily rates precisely because that is where one session can undo months.
- Two rules follow: don’t open trades in the zone, and don’t let one age into it.
The speed of risk has a name
An option’s delta tells you how stock-like your position is right now. Gamma tells you how fast that is about to change.
Far from expiry, gamma is small: the stock drifts, your position’s character changes slowly, and you have time to react. Close to expiry, gamma grows violently for strikes near the stock price.
Gamma is how fast your risk changes character. Far from expiry the curve is nearly flat. In the final stretch it goes vertical — the same position, on the same stock, becomes a different trade. Shape is illustrative; the boundary is not drawn to a specific number of days.
Practically: a short put that was a comfortable, high-odds winner on Monday morning can behave like a full stock position by Tuesday afternoon after an ordinary down move. Nothing about your thesis changed. The odds you entered with are simply no longer describing the position you now hold.
That late-life region is what traders call the gamma zone, and it is the single most common place where a good income record goes to die.
Why the yield looks so good there
Time decay is fastest right before expiry, so short-dated options pay the most premium per day. On paper this is irresistible:
The same $100 of credit, annualized two ways
| Held for | Credit | Annualized | Room to react |
|---|---|---|---|
| A few days | $100 | very high | one session |
| Several weeks | $100 | modest | weeks |
Annualizing a few days of premium produces a spectacular headline rate. The mistake is annualizing the reward without annualizing the risk: you are being paid those rich daily rates for standing exactly where one bad session can take back months of income.
Riding a short option into its final days is picking up the last few coins in front of the steamroller.
The engine’s two rules
- Don’t enter the zone. The scanner holds a hard floor on days-to-expiry for new trades and will not surface entries inside it, whatever settings you choose. There is a modeling reason as well as a risk one: our tail model asks where the stock ends up at expiry, and inside the gamma zone the path — not just the destination — is what hurts you. A model that only scores destinations would be quietly overconfident there, so we decline to use it there.
- Leave before it closes around you. Trades you already hold do not get safer with age — the zone comes to you. The exit guidance in the app includes a time-based checkpoint a few weeks before expiry: by then most of the credit you were owed has usually been earned, and what remains is increasingly gamma risk rather than income. Take the win, or roll to a later expiration.
The trade-off, stated plainly
This rule costs money in calm markets. Those final days really do decay fastest, and a seller who harvests them through a quiet year will out-earn one who does not. We accept giving that up in exchange for never being in the position where a single gap decides the year. That is a judgement about survivability, not a claim of superior returns.
Where to see it
Every opportunity shows its days to expiry and its exit checkpoints alongside the credit, so the timeline is never implicit. If you want the mechanics of how the expiry-day distribution is modeled — and why that model is untrustworthy near expiry — that is in Methodology, under limitations.
Next lesson
9. What a covered call really costsThe premium is visible; the upside you give away and the tax bill if you're assigned are not. We model all three.Educational information only — not investment, tax, or legal advice. Nest Money is not a registered investment adviser or broker-dealer. Every figure and diagram in this lesson is illustrative. Options involve substantial risk of loss, including loss greater than the premium collected.