Yes, that's the point; it takes years for people to reach the peak in their chosen field. I'd say at least 10 years in my area and I'd assume it's the same in IT etc.
Again, it's trade specific. I know Google are big on academic achievement first for their engineers (the DIT figures above are depressing) but like to take the best of the best (as it were) from college and have them fresh to fit into the google culture. Similarly, they'd take a manager with an MBA over managers with no academic background and experience in most cases.
I think the construction boom just had too much to do with losing skills, so many industries built up around it or were riding the coattails that we were just too narrow in our education.
Ironically, some of the surviving construction companies are starting to do ok and are recruiting. I was talking to a few yesterday and they're facing a massive problem in that they can't recruit Irish engineers with experience because they aren't here anymore and don't want to come back. They're having import skills.
Just one last note to keep the sweeping generalisations going. I recently had call to use an Irish carpenter and Irish plumber. The work was second to none (carpenter even came back a week later as he wasn't happy with the way he'd installed a runner and it had been bugging him. He basically took out a whole unit and did it again even though we thought it was fine).
This is alonge side work that was done via foriegn labour where we had to keep getting them out to fix several issues over and over. In the end, the plumber even offered to fix some of it while he was there.
So, it's pot luck who you get. But every trade and every skill has it's good and bad irrespective of nationality.