Suddenly, as I was lecturing away in my finance course, it occurred to me, and I blurted it out: Bonds are different from men because bonds eventually mature.
(unless they are perpetuities, which, while they do exist in the real world, are mostly used to introduce present value concepts in the classroom)
btw, I deeply resemble this observation (as must be obvious to anyone who has read more than two three items on this blog). What is more, I am generally pleased about it.