Q. about not connecting warp points

[PvK]

Unless it's a High Tech game, your opponents will need to do a lot of research and then construction to get warp point opening technology. Distance to other systems is also a factor. In general, it's probably a pretty safe system, for a long time, anyway.

PvK

[dogscoff]

I believe warp points can also be created by random events. I've certainly seen them destroyed in this way.

These are incredibly rare though - in two years of playing I've only seen it happen once.