Change max fire time

[Snave]

Hope someone here can help me out. Recently my therion 166 has developed a problem where the fire button will frequently stick when pressed causing the mod to fire until I realise and pry the button out. 

The mod has an auto cut off at about 20 seconds and I've been looking for a way on escribe to manually change this to a lower number so I stop wrecking my cotton accidently. 

Does anyone know if I can change this or where the setting is? It seems I can change everything apart from this setting!