I'm not going to say that a plastic trigger on a RWS (or any other make/model) air rifle couldn't ever break. But I believe that most of those stories are just that, stories. Probably from people with an axe to grind with Diana "because there is a plastic trigger blah blah". Lets face it the firearm (and airgun) industry has been using "plastic" for years and when was the last time you heard of a Glock pistol failing. And that was the scare tactic when the polymer (Plastic) framed auto pistols started to come out. People said they would melt in the heat, crack in the cold and wouldn't last among other things. The factory spring guides in most air rifles are plastic (some form of synthetic). I would think that that guide would be subjected to more stress over potentially thousands of shots then the trigger or safety tab ever would. They use them for cost and weight savings, but I don't believe they are any more prone to fail then a alloy casting. Just my opinion.
Nathan