protecting white cedar shingles


I have white cedar shingles on my house. 10 years ago when we put them up, we treated them with a stain/bleach mixture, and they have weathered to a fairly uniform gray color (not quite Cape Cod, but that's 500 miles away), which is what we wanted.
The most exposed side of the house is showing a fair amount of weathering (wood surface eroding), and I would like to slow this down by applying something. Question is, what? The main thing I would like to achieve is some water repellency, and I would like not to create a seriously blotchy effect. The shingles are going to differ quite a bit in the degree to which they absorb anything I apply.
So, advice?
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Cabots oil products are good
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