I just joined here and after reading this, my first discussion, I have a comment. In my little garden, I mulched the 2' pathway with straw, which held up for at least 2 years. I'm wondering whether or not in your case, if you did this, then in subsequent years you could just add weeded out plants to the straw, etc. Then you could move the planting beds over so one of the adjacent growing beds would become the new pathway for a couple of years, and so on. This would allow for crop "rotation" to a degree, which should be good for the plants. You could still use your 6' covers - but you'd have one bed exposed to the weather for a while until it was again used as a growing bed (that's perhaps a downside, but maybe the frost would kill some undesirables(?).