Permissions are for one term only.
Almost without exception, publishers grant permission for a single term only. Therefore, even if your syllabus does not change one iota, you must still request permission each semester. Because obtaining permissions is often a lengthy process, it is advisable to allow two months from start to finish. You do not have to submit the actual readings on these dates if you have not finished assembling them, but it is not a bad idea to do so as soon as you can. For one thing, compilations, such as the ASHE Reade r, require us to send requests to the author or the original publisher, and we often need to refer to the article for this information.