Although Nasib has a point I would never advise a student to complete a whole IR course in the aircraft. 35 hours sim may be too much, however the sim still has its uses. For example: you cannot freeze a flight in the aircraft to see what is going on, you cannot plot the hold that has just been flown and in the sim the instructor has the ability to decide what 'curve balls' to throw at the student to see what they can deal with. It is all about getting the correct balance between sim and aircraft.