That depends on what you've done before the PhD studies, and what you do meanwhile. The PhD thesis itself takes about two years in Sweden too, including the research for it and some time for teaching and such. The first two years of a customary four year PhD programme in Sweden consist of the Lic thesis, which is a separate project from the PhD thesis (even though they're usually on the same subject).

Those who spend eight or fifteen years do a lot of fluff on the side, like working.