The best way to see if a program is right for you is to set a goal at the beginning, to note what you do at each session such as weight used, rest periods and sets. If you are making progress, then the program is right for you. If you are no longer making any progress, then it is time to change. In general, you can keep doing a program for 6 weeks, after which you may no longer make any progress. In fact, the first week is used to adapt yourself to the weights and get your bearings. If you give it all you've got, you'll gradually increase in power. Usually after 6 weeks of doing the same routine, stagnation can occur. If you give your training a change in repetition and routine, you will succeed better in improving your muscle abilities and, therefore, you will never stagnate.