how deep will we go?

I'm reading an announcement from October last for the 2010 Mining Resources Presentation. Amonst other news covered, Salebury is mentioned in a very favourable light... eg;

Salebury
Significant resource potential with
numerous high grade intersections
including:
- 48m @ 2.18% Cu & 1.97 g/t Au
- 42m @ 1.24% Cu & 0.79 g/t Au
- 30m @ 1.93% Cu & 1.25 g/t Au

Very attractive grades indeed. However, what interests me is on the 'cross-section' map is at the bottom right-hand corner, it states "No mineralisation beyond 135m". The drill holes go to a depth of 170m and that's it. Does anyone out there know if it would be viable for us to go to a depth of say, 600m or more? Who know's what we'll discover.
Any Geo's with any historical knowledge of that area like to enlighten me?

Thanks,

MTW