I'm no lawyer but I hold several patents. And what it really boils down to is how broad is your claim. The broader the claim, the more likely you can go after infringers. The broad claim of "a slant", versus a narrow claim like "a slant of 30 degrees". I can get around the latter claim by making it a slant of 35 degrees but I don't get around the former claim.

Currently Segway is suing some hoverboard manufacturers for infringement and if you read Segway's claim, it is pretty broad. Again, I'm no lawyer but I think Segway has a pretty good case.

So as time moves on with a technology, it is harder and harder to get a broad claim because it has already been done. So you make you claims more narrow which then are easier to get around.