Patents issued by all patent offices have a finite term during which they can be enforced. For example, in the U.S., patents that issue on applications filed after June 8, 1995, can be enforced in the U.S. for a period of twenty years after the effective filing date. If the invention is at such an embryonic stage that products that embody it will not be on sale for an extended period, the patent owner may be able to prevent others from practicing the invention for only a short time - thus, reducing the commercial potential of the invention. Consider how much of a 20-year patent term is likely to be consumed before products are available for sale.