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Since I've had people ask me about this a few times over the years, I thought I should document my weekly process for keeping my GPS current with active geocaches. Well, mostly current anyway, since I go through this once a week, or less often if I'm not feeling sufficiently motivated.
This is my normal day-to-day waypoint load for my GPS and it gives me a lot of caches in the area, in places I might go spur of the moment. If I need caches for someplace outside of my regular PQs, for example, I'll load my GPS in advance specifically for that area.
I don't suggest that this is the ideal process for everyone, because it can't be, but it has worked very well for me. If you're looking to do something similar, you'll want to take into account your own personal caching style and needs, your geographical area and cache density, the specifics of what your GPS can store, and so on.
My process is used with my Garmin 60Cx (and a 60C before that), and utilizes both GSAK and MapSource.