Yes. The human body is amazingly adaptable to any situation, environment, or stimulus, and one area where this adaptability presents itself is in your training. So doing the same training program over and over will decrease the amount of adaptation or gains your body makes in response.
Changing your training program in a planned and progressive manner (periodization) on the other hand keeps your body guessing so you'll experience more dramatic changes as a result. When you take a look at what a periodized program is, you'll find that it actually takes no more time to do than what you have been doing. And since you will be making more gains for the same amount of time spent, it's actually more time effective.
Here's a simple way to periodize your training: Alternate three-week phases in which you perform three sets of 8-12 repetitions in the first phase and four sets of 4-6 repetitions in the second phase. Adjust your weights accordingly so you'll use lighter weights for three weeks and then heavier weights for the next three weeks. This approach will help you increase strength, raise your metabolism, and improve muscular endurance.
-- Craig Friedman, Performance Specialist, Athletes' Performance