One you stain and treat it with a sealer, it will absorb these but,pressure treated or not, once you neglect wood for 4 years it neglected.
You need to apply a waterproofing sealer to a wood deck at least once a year to keep it looking good.
You could try Minwax Helmsmans Spar Varniah to polyurthene coat the deck use a satin finish. This may last longer than a year. However, I never heard of anyone doing it.
You know what they say about opinions.
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