The twenty-year term is a maximum, not a guarantee. From year three, an annual renewal fee keeps the patent alive; the fee rises as the patent ages, which is deliberate — it forces holders to ask each year whether the protection still earns its cost.
What this means in practice
- Someone must own the renewal calendar; lapsed patents are usually discovered too late.
- A lapsed patent can sometimes be restored within a limited window, but restoration is discretionary and conditions apply — prevention is far cheaper.
- Letting a low-value patent lapse deliberately is legitimate portfolio strategy; letting a valuable one lapse accidentally is a tragedy.