Cheer up. One day, probability ensures that one of them will be correct, if we live long enough. Truth is, that is exactly the way fortune telling works. Tell enough fortunes and odds are some will be correct.
My experience with technical jobs is that 5 years does represent sort of a dividing line. After 5 years your odds of becoming a lifer increase sharply.
I think it is generally good advice to change jobs a few times while one is young. Large companies in particular tend to pigeonhole technical employees, depriving them of the opportunity to broaden their skills. Employees who have been at a number of companies tend to have broader experience from both a technical and a management standpoint. Employees who have worked for only a single company are more likely to get trapped in a "we've always done it that way" paradigm.
I think his strategy is to make Texas look better by dragging all of the other states down. Has anybody taken a look at the Texas report card? We rank worst in almost every category from high school dropouts to most children without insurance to lowest education ranking, etc. It's pitiful. The only thing that could improve that is to make all of the other states suck too.
My GP here in NY told me the same thing. Twenty pounds overweight and she told me I couldn't be her patient unless I lost the weight. I lost the doctor instead. Sure, I need to lose the weight, but I a) don't need an ultimatum from someone I really don't know and b) don't want a doctor that isn't taking anything but "safe" patients.