Good discussion point - I can absolutely see the merit in it. He's only 23 years old and is the most damaging forward in the game - they've locked him down and got rid of any future bidding wars. It's particularly astute given the salary cap will increase over that time (though I'm sure there will be clauses covering salary cap rises or falls). Also gives the Cowboys a real base to start some real long term planning with their most valuable asset locked in. And for the player, it's long term security and allows him to simply focus on the job at hand.
However, there are some obvious and not so obvious risks. The biggest and most obvious risk is if he becomes injury prone, which given the position and style in which he plays, is quite possible, they're stuck with a very expensive lemon for a long time, and could ruin them for many a year (The Raiders are only just recovering now from the decision to tie in Campese on a very expensive 5 year deal they agreed when he was firing on all cylinders - the next season his body fell apart). Their only way out of this scenario would be to medically retire him, then insurance would pay out, but if he doesn't want that, they're screwed.
The other obvious big risk is that he simply does not hold his current form and status for that period of time - which again is quite possible.
Then then not so obvious risk is around his motivation - you often see players have their best seasons in the years that they're coming off contract - they know they're in the shop window and potentially without a job if they don't perform. With this type of deal, he can get real comfortable - it will take an enormous amount of self discipline for him to be 'on' for the full 10 years.
In summary; it's a big risk, but they have just secured a 23 year old beast - If I were a Cowboys fan, I'd be content with that and not too worried about the long term risks.

Please don't burst my bubble!

Yes, new 10 year deals for McDermott and Walters

I don't really see the point in it, except for PR and to let other players know he's staying. If the Cowboys don't have some serious get-out clauses down the track then its insane. Whilst he may have traded some salary its unlikely to be much given he could probably have got top dollar for at least 4 years from somewhere else. So if he doesn't retain his standard he could end up being seen as a massive albatross on the club as a whole. We've seen that happen with other players, albeit over shorter terms.

Is £50,000 the face-saving fee we should all agree GH secured in the end?

In other words, 20% of what he was demanding?

Cool.

Who knows? Latest on the Cronulla fan boards is that the NRL let Cronulla pay a fee for him without it counting on their Salary Cap, just like they did when Souths got Burgess back from RU.