My DCs had an 11 plus tutor, for 1 hour per week from 12 months before the date of the 11 plus, backed up with some extra practice sheets at home nearing the time (approx 3 months before). It all depends on how they are scoring on the papers though and how close it is to the test. I found scores really shot up approx 8 weeks before the test, and we would get them to do 2 practice papers per week on top. Had they been scoring low marks 2 months beforehand I would have considered a tutor, but once they know the trick of how to answer the questions, it's just practice really, and I don't see a tutor as much value from then on. I found it was about practising and getting the speed right.