Anyway, in this month's issue, in among advertisements for an independent school, a bespoke ("tailor-made", as they put it) sofa manufacturer and (tut tut!) a ringtone service, is the following:
Hmm, my younger daughter has 11 years' experience, or perhaps 11 years of experience, in English. She probably wouldn't know that there should either be an apostrophe after "years" (because the experience belongs to the years) or the word "of" after it (because the years are the duration of the experience); I suppose I therefore shouldn't be harsh on someone who has only 7 years' experience. Then again, she doesn't have a TESOL certificate...