It depends - partly on the job, and partly on the individual. Assuming, first, that two years' training is really necessary - not in theory, but in practice - and secondly, that the individual in question will want to retire at 65, you may be able to justify different treatment on grounds of age ('objective justification': see questions 27 and 28, below). But the test of objective justification is a stiff one, and you will have to be able to produce evidence to back your assertions. Take legal advice.
