Getting CI Instance

[eluser]Unknown[/eluser]
Hi. I learned from CI self libraries that they're getting an instance of CI with

Code:

$this->CI =& get_instance();

So I used it too in my Libraries and now I'm using them in my plugin system. I noticed that each instantiating of CI cause to inherit the whole CI which is a usual thing But I wanted to know is it harmful to getting too much of CI instances and be effective on the system running speed.