No matter how many times you say this, it isn't going to be true.yup, going by skills, it should take about the same time length to get through all the campaign missions in GTS than previous games at launch.
If you're talking about going for gold, the license tests in past GT games would easily equate to at least half the time it'll take to do stuff from the campaign in this game. And the go-to GT game some people like to compare this to due to a similar car count and it being the first one on a new system (GT3) that was suposedly light on content, had more tournaments than the number of missions in challenge mode alone.
Bring GT4 into the equation and it's not even a comparison, as it had a special mission mode on top of the career mode, which is basically what the challenge mode is derived from to begin with. Challenge mode is not a "new take", It is an extension of GT4's missions, and GT5 Prologue's events.