Loose home button on my iPhone 5 (Verizon)

I've recently had my iPhone 5 replaced (about a month ago) by Apple under warranty due to a very loose home button and an odd rattling noise coming from inside the phone. The Genius at the store told me that they could replace my phone, but he couldn't guarantee that my new phone wouldn't have the same problem. I thought that it was a very concerning issue, so I had them replace it. Now, I've been noticing that my home button is wiggling, and it's bothering me every time I want to click it because it sounds strange. It's not unbearable, but annoying. Should I take my phone back to the Apple store, and what would they do for my situation if I did? Would they just replace my phone again, or would they open it up and tighten it? Does all of this go under warranty even though I've already had a replacement, and would a Genius opening my phone void the warranty? My iPhone was such an investment, I it is absolutely crucial for there to be almost nothing that could potentially defunct the phone.