it all depends on your targets
the fast trak IR (10 days or 14 days) is a very demanding training that you should chose if you dont have any opportunity to fly often and you want to concentrate your flight in one shot.
but if you have time and aviation is your career I dont see the point to do IR as fast as you can... on the contrary you should take as much time you can afford because this phase of your training is probably one of the most important... if you like the instructors and the syllabus just ask the training provider a more suitable pace.