I "refurb'd" mine some 12 years ago by laying the vinyl-clad composite boards (of the same width) over the older redwood, which was showing wear, but still good. It looked ratty. I also replaced the redwood hand rails with these composite boards, and overlaid the steps (there's 9 steps up to it from the ground, bi-level house). Today it still looks new!
This has turned out to be the best decking decision I've ever made, and if I had to do it all over from scratch I'd use treated lumber under the composite again. It doesn't have to be re-done any time soon.
It's not the Trex brand: that type of composite only seems to last about 12-15 years. I was forewarned about that by a friend in the construction business when I did it: I used the Veranda brand.