By the way I know you're all wondering so I took some official measurements for how far Stun Lancers are able to run and use their attack in a single turn. When you adjust for the additional square afforded by the slash ability it comes to... 850 trillion miles.

They're relatively easy to deal with though, bear in mind that Viper tongues go twice that far and through surfaces such as walls, shipping containers and the molten core of the planet.