MM, I certainly cannot answer your question from personal experience as an athlete.
But I have noticed that Charlie White's favorite expression after a competitive performance seems to be, "We left it all on the ice." (Often he relies on his mantra in the context of saying that D/W themselves believe that they could not have skated any better on that particular day -- whether or not they received some Level 3s or whatever.)
So whatever the totality of "it" means, I guess the question -- at least for D/W -- is how many rapid cycles of leaving it all on the ice and then restoring new supplies of it inside themselves (whether that process is deliberate or unconscious) they can manage during the short number of days spanning the team event and their own discipline.
Sorry if my example sounds silly. But I don't mean to be facetious.
I think the issue is bigger than the physical feats of landing quads or executing other difficult elements. I think that White is referring also to summoning the mental strength to give a successful performance.
Maybe the concern in terms of the mental demands is that the team event could cause a "hangover" analogous to the phenomenon of Olympic "hangover" that leads some skaters to skip Worlds a few weeks later -- or to the apparent Worlds "hangover" that seemed to result in some skaters bypassing WTT. And many of those who did compete at WTT commented on how tough it was to do so.
Very true about the word hangover!! Skaters complain of dealing with hangovers at post Olympic worlds which is a month later!!! Some are certainly already talking about athletes at the Olympics leaving their Olympic performance in the team event and not their discipline event. North American skaters hate the 4cc competition before the Olympics if they're going!! Lol now there's a 4cc at the olympics !! Like d/w to leave it all on the ice in Vancouver said no to 4cc in 2010 and will likely do so again in 2014 and not even do the team event.