I review my someday/maybe weekly, and those are items that may not happen up to 6 months. I also have an annual review list that I review in January every year; these are bigger projects that I may decide to move to someday/maybe in any certain year.
If you have a project that you can assign a next action to, and you may or may not find time to work on it, then I would go ahead and make it a project and assign a next action. Often these will get acted upon, even though you thought you may not have time. Especially if the next action is something simple like a phone call.