The posts you snap onto vibrate loose over time, yeah. I've lost one and fasten the "bra" to the grill with electrical tape on that corner. I agree with using Loctite on them if you can. I just tighten them up once a week or so. I only keep it on Thanksgiving to Easter anyway, so just a few more weeks to go,
I've got them on all of my C2's. I put a small washer and nylon locknut on the backside of all four corners to keep the posts from coming loose. I've found that after a few years the studs start to corrode and the winterfronts don't "snap" on as well, so then it's either replace them or make a slight alteration to the winterfront with a paper hole punch and use zip ties. I liked the system on the FS-65's better!