How many title defences before superfight?

It used to be the superfights were going to be for fighters who'd cleaned out their divisions (Anderson Silva, GSP, Aldo).

Now...

* Pettis hardly defended his title before he wants Aldo

* Weidman wants Jon Jones with 1 title defence

* Hendricks wants Weidman after 2 title defences

Courage is great, but don't superfights have more value after cleaning out your division?