If theta decay were a straight line, the long-options business would be simpler. It is not. The decay curve is one of the most consequential - and most misunderstood - concepts in options trading.

What the curve actually looks like

A long ATM option with 60 days to expiry loses about $0.03 per day in time value. The same option with 14 days left loses $0.10 per day. With 5 days left, $0.25 per day. The curve is steep - and it gets steeper.

Why the curve matters for entries

If you are buying long premium, your worst entry zone is the 21-30 DTE range. You are paying for time value that is about to bleed at an accelerating rate, and the move you need has not yet expanded enough to overcome the bleed. Either go shorter and accept gamma risk, or longer and pay for more cushion.

Why the curve matters for exits

If you are selling premium, the last 14 days produce most of the income. Selling 45 DTE and rolling at 14-21 DTE is mathematically efficient - you are collecting the steepest part of the curve and avoiding the worst gamma risk at the end.

The trap of the last week

In the final week, theta becomes brutal but gamma also explodes. A 0.40-delta option can swing to 0.05 or 0.95 on a single session. If you are short premium, the gamma risk can wipe out a year of clean income on one bad session. If you are long premium, you need a sharp move or theta eats the position whole.

The honest takeaway

Treat the option's life as three regimes. 60+ days: slow, vega-dominant. 14-60 days: balanced. 0-14 days: gamma- and theta-dominant. The strategy that works in regime one will fail in regime three. Plan the exit before the entry.