This is based on a Quora question.
There are a lot of potential meanings to the phrase “dynamic patent monopoly lengths,” but by one definition, they may already exist.
Most patent offices in the world charge some type of “maintenance fee” at regular time intervals after a patent is granted, or even while pending in some cases. Failure to pay such maintenance fees results in the patent rights expiring before the theoretical “full” term of the patent or patent application.
For example, in the US, maintenance fees are due at 4, 8, and 12 years after the patent’s grant date. If the all of the maintenance fees are paid, the patent will have a full term of 20 years from filing (or 17 from issuance, or as adjusted by patent term adjustments, or as modified by a terminal disclaimer, etc. – it’s complicated).
Only something around 50% of patents are maintained for their full terms (see:), so the rest only have a term that is as long as the maintenance fees are paid. Seems like a “dynamic” length to me.