I use a similar structure to you Derek with the following folders to contain all my individual projects
- Priority Projects
- Main Projects
- Held Projects
- Someday Maybe
My projects are pretty fluid day to day and many of them frequently move up and down my folders as I reschedule my workdays. The projects I plan to work on either today or tomorrow move into my Priority folder and they appear at the top of my lists. I try to keep this group to a minimum usually no more than four or five critical ones to make sure I keep them moving. This week / next week projects tend to be in Main and I usually have about 20-30 in here.
Projects that are still on my radar but that I don't plan to move on in the next week or so drop into Held, I usually have between 50-75 in here.
The ones that are 3-6 months and beyond stay in Someday Maybe. Some of these in here are physically put on hold, so I see the paused icon, which gives me the visual indication they are very low priority. Others in here are given long start dates which gives me a clock icon on the project. When they become available the icons disappear and either weekly or monthly I give this list a quick scan to see the ones with no icon and give it a quick review to move them up to one of the other folders, pause them or reschedule a new start date to bring them up again later.
During my weekly reviews I will also review most of these projects as their review period triggers. The ones on hold and also in someday maybe tend to have their review periods pushed out to between 2 to 12 months depending on the project.
In addition to my weekly reviews I also tend to quickly browse my project folders every evening and review the Priority and Main project lists, picking my top 3-5 projects to move into Priority etc. At weekends I also give the held and main list a quick scan to see if something needs promoting or demoting for the coming week.