Yes, once it is drawn out nice you can use it for about three or four years, it dos'nt seem to get as dirty as foundation, then scrape off all the wax and give it back to them to start again, sometimes you have to hose it with pressure washer. It never gets holes in it, but you should never put it in a solar wax melter, but we won't dwell on that.
Yes I use it in my Langstroths. When I first had my Poly Langstroth everything was new including the plastic foundation. I had to heavily feed the bees to help them draw the comb out. Once it has been drawn it is just as good as normal foundation but much more sturdier in the extractor. When the comb becomes darker with use I carefully scrape off the old wax and paint the foundation with honey so the bees begging to draw the comb. If need bee I would help them with feed. I suppose its a way of saving on having to replace comb when its old.