From what I've read, in the US a patent is valid until 20 years after it is granted, retroactive to the date that it's filled. That can be a 40 years interval, or more, if the USPTO don't do it's job well (and I know of patents that did go over 30 years).
From what I've read, in the US a patent is valid until 20 years after it is granted, retroactive to the date that it's filled. That can be a 40 years interval, or more, if the USPTO don't do it's job well (and I know of patents that did go over 30 years).