I used small dabs of blue Loctite on all accessories - rear rack and the bottle cage. It may be superfluous since I've also added a plastic under-cage mount for my Topeak frame pump. That probably adds a little resistance to vibration.

But I recently checked the bolts for my month-old rear rack and discovered a couple of slightly loose bolts. So even the dabs of blue Loctite weren't unnecessary. I probably should have used more. One of my accessories came pre-coated with blue Loctite on the bolts - pretty much the entire threaded surface was coated with blue Loctite. So I'll probably redo my other bolts and use more Loctite.