Maybe 20 years ago it was -- the yard had a fair coverage of dandelions; the chemicals I tried didn't kill them, not at the strength I was using it at, and I didn't want to use anything stronger.
So I got one of those probe-things for dandelions, sat down in the yard, and started to work -- maybe two hours a day, for a week or two. Got 'em all.
Kept a watch out -- every day I went out to catch any new ones.
(That was in the summer (of course))
Anyway, the next summer, still had them, but no where's as many, and got them too, by hand.
Fewer yet the third summer.
Since then, very, very few.
And the adjoining yard in the back (with a sheer-wall between us, their yard is 4 or so feet lowere than ours), they had lots of dandelions earlier this summer, and they bloomed and everything, but strangely no problem came from it.
Anyway, that's *my* experience.
David