The duration will depend you how quickly you are able to clear each level. Normally it will take a minimum of 3 to 4 years to complete the course.
You need to begin with enrolling for the CPT level first. On clearing this level you can enroll for either one group of IPCC or both. On clearing one group you can enroll for the article ship training for 3 years. Along with this you need to complete orientation course of 35 hours and 100 hours of ITT training. On clearing both the groups you start preparing for the finals. You can appear for the exam six months prior to completing article ship.