Thanks for bringing up a good point about patents. While a patent has exclusivity time limit on infringement, it remains forever to protect a working inventor using the patent established now as PRIOR ART forever.
This means no one else can legally re-claim patented prior art already established as now their own, and later demanding fees or shutting out the inventor from continuing an established business.
It certainly does not protect them from competition once the patent expires, so they have 25 years exclusivity to make hay while the sun shines, then it's a free-for all. Hopefully the inventor has moved onto new technology/IP by then, but in the case of simple and important inventions the expiration of the patent brings an end to their profitability as the clones flood the market.
In practice most patents can be worked around by variations on the theme. It has always interested me that you can't patent a recipe (for food) and yet the restaurant/food industry is doing very well thank you
digifish