Why are patents protected of a limited period of time?

Question

Does this argue in favor of not patenting a item?

Answer 1

Patents are a way to incentivize companies to invest in research and development by allowing them to recover those costs over a life of 20 years without having to compete with companies who just copy the patented product and sell it at a lower price.  There is no economic reason for not patent-protecting a product that has incurred significant development costs.

Answer 2

If you're in the US, the answer is because the Constitution requires that the Congress limit the amount of time an invention be protected (the same clause limits copyrights, too). The purpose of the patent system is to promote innovation by granting a temporary "monopoly" over a product in exchange for disclosing the product to the public.

Even though it's not in perpetuity, there are still plenty of reasons to get a patent. For instance, many products become obsolete well before the patent expires (think computers). Also, the temporary monopoly during the 20 year life of the patent (from your filing date) helps build brand recognition for your product, and could establish your company as the leader in that market. Moreover, with a patent, you can be the only company that profits from your invention for 20 years from your filing date. If your product is successful, you'll have competition copying your product. A patent will help you stop people from copying.