Welcome to SMF! The answer to your question is that it is your choice. Some do, and some don't. If you are new to smoking please check out Jeff's 5-day ecourse. Also, go through the Charcoal and Wood Smoker sections of the forum. You will be able to check out procedures, modifications, and techniques that are specific to many different makes and models of smokers. At that point you will have some good information that may help you. If not, keep asking questions, the friendly folk here will make answer.
Take care, have fun, and do good!
P.S. - It would help us to answer your questions if we knew the make and model of your offset.