my broiler cover and drip pan/sear plate both have lots of surface rust and have since early on. I don't think they're actually going to fall apart or sauce a real issue anytime soon, and I'm grilling 2 or 3 times a week year round. Not quite at a year yet, I'd love to buy replacements out of 316 steel, which would possibly last forever (Titanium would be cool, but not worth the expense). I saw a stainless replacement somewhere, I think Amazon, but there were complaints about warping and I'm sure I'd get them too because I like to run my grill as hot as I can when searing.
At the price I paid, my 700FB has been excellent. It is capable of doing a decent job of almost anything I can think of and room enough to cook for a party or family or maybe work. the rust isn't very enticing but hot grills with acid/water/salt/iron (from heme, foremost) will break down most steels that aren't rather specialized and I'd have to have paid more for a more premium steel. I would buy the parts now iff the price wasn't crazy, but for now, I'm just going to cook on this thing indefinitely.