I have a deck made with Trex decking and PVC railings. Not my 1st choice, but it came with the house and looks good. We have done nothing to it aside from spray it down a couple times in the last 6 years.
I just finished with a power washer and man does it looks great. I doubt I'll need to touch it again for a few more years. In the $$ vs time debate, so far, I'm winning.
the PVC railings, however attract moss and gunk and need to be washed (bleached) a few times a season.
My experience, YMMV.