RE: Longonzinc re royalty effect I will respond to a couple of points. First, the 900 Au and 2.5 Cu is just an example of cash flows at those price points and it shows real cash flow. As far as I can tell no one has a magic ball that can tell for certain what future metal prices will be. I think the price points above would make for a dire situation. However, what I think you are trying to describe if free cash flow. With the high debt load they have, they need to generate more cash flow to service their debt than they could generate at those prices.
Almost any realistic way you project future metal prices with the mine production and cash costs as forecasted by TCM there will be similar payback periods for the initial capex for both TCM and RG, thus the profit points realitive to payback will be similar if they achieve the operational goals they've established. I tend to look at metal production over the first 5 to 7 years, mostly because that is the sweet spot, as well as the period in which most projects are paid back. Years beyond that is typically where the "profit" comes from. However, depending upon the ore body the mine plans beyond say 5 years can change significantly (for example higher grade ores are discovered and mined plans get changed [less likely in this case]).
As far as risk, yes there is always risk that metal grades and recoveries will not be as modeled or that operational costs will be higher than projected or combination of all of these factors. When a project like this fails all involved even RG will feel the pain.