I'm putting on my FR clothes, too. <\flame on!>
With a straight rear axle, like our trucks, the rear tires should never need rotation. Unless you over or under inflate, which is a different discussion.
The front tires can wear on the edges from steering and caster and camber angles. When that happens, you can swap with the rears to do two things:
1) Move the most evenly worn tires to the front for best steering.
2) Move the weirdly worn tires to the rear where they will be held in a straight path and wear off the high spots to make them more evenly worn over time.
And if the spare is the same size, it can be rotated in to get full use out of the rubber you paid for.
We used to figure on rotating about every 20K miles, expecting more than 60K of useful life. It wasn't uncommon to pull the wheels off junked cars and keep on using them.
Softer rubber and more extreme suspension geometry seems to be in vogue these days, so maybe tires are wearing faster, but I'm not buying 3,000 miles, that's just crazy. Even 6,000 doesn't sound reasonable to me. If my truck was wearing out tires that fast, I'd be looking for ways to fix the problem.
<\flame off>