Most often, the same people who talk to you on the phone control the seminar logistics. That means if they are sloppy or hurried on the phone or do not return your call, that will be the same service you get at the seminar. They should be able to clearly let you know if you will be able to achieve this outcome or not during the training. If they cannot accommodate your requests, ask them if any other NLP institute that they know of specializes in this area. Longer DOES NOT mean that you'll learn more material.
Balance is the key.
Consider quality before quantity of training time. Also consider class hours, but only briefly, because it really is not that important. A 14 day program that meets every day from 9 am - 9 pm is around 140 hours. A 28 day program that meets 9 am - 4 pm and has weekends off will compare at approximately the same classroom hours. One class is fast paced, one is slower.