Yes, but after 20 years you’re not at square one, others have free reign to use and abuse your expired patent. Sure, you can tacticize patents in a way where you make a starting patent, then before it’s about to expire “expand” it with a new one in a way which invalidates use of the previous, but I don’t know if that “loophole” is patched and if not, how it looks in real life.
Yes, but after 20 years you’re not at square one, others have free reign to use and abuse your expired patent. Sure, you can tacticize patents in a way where you make a starting patent, then before it’s about to expire “expand” it with a new one in a way which invalidates use of the previous, but I don’t know if that “loophole” is patched and if not, how it looks in real life.