Expiration in Two Days: Science Fiction

I expire in two days. That's been rough to adjust to. I mean, I always knew I'd expire someday, but I never actually went around hunting to figure out my expiration date--that's not in my nature, or so I thought. I didn't find out what my expiration date was until another me tried to kill us. Then I had some serious reason for wondering why and what I needed to do to protect myself. Turns out, not much. Not getting killed for two days is something most anybody can handle. The real question is why somebody would try to kill a person expiring in two days anyway. Sure, I've heard the rumors about the transformations some of us make when we start to expire, but it never really made sense--

Inspiration: Checking when library holds expire.
Story Potential: High?
Notes: I guess it's high potential, because I really want to know why somebody would try to kill him. Of course, my brain could always come up with a stupid reason that would make this a low potential story.