Refreshing Stain on Cedar Fence

I want to refresh the stain on my 80 foot shadow box cedar fence instead of stripping it because the stain is just faded. On the shaded side, there is no flaking and only a few small spots of green algae. On the sunny side, there is more fading and minimal flaking on a few boards. I want to use either Armstrong Clark (ease of application)or TWP 1500 (wood preservative and mix of synthetic and natural resins), but I originally used Olympic Maximum Cedar oil based. Can I switch without stripping? Or should I stick with the Olympic Maximum oil based to which I still have purchase access? What is your estimate of gallons needed, as I must order on Internet if use AC or TWP. Thanks.