I would go with a 5 wheel rotation.
You reduce the wear rate of your tires, and if you get a flat the "spare" becomes a "regular" tire.
If your tires are worn half way, you are stuck buying 2 NEW tires to put on the back "axel". So it is more $$$.
But what is more of a pain is they might not have your tires in stock, or they are discontinued at that point.
After a flat happens, then a brand new tire sits in the spare well. You can then make it a different tire completely, one that maybe you plan on purchasing in the future as your full time set.
I was thinking of doing a fifth wheel rotation at one point with a tire that would stay in my storage locker as I have a small spare.
That way if you have a tire blowout, you aren't shopping for a full new set.
And your tires wear is reduced by 25 percent by adding the fifth tire into the rotation sequence.