Number of spare tires

That's the exception, not the rule. If I have to carry more than one spare tire, I might as well own a half track.

I had a blow out last year and the shrapnel from the blown tire snapped off the valve stem an the wheel in front of it, so there I was with 2 tires down. :(

I only carry one, and since flats are so rare, I have it stashed under the bed. Because I don't plan on needing it.

Finding the right tire is usually much more difficult than finding someone to mount it. So I would go with carrying any extras unmounted. It will be lighter and you can still stuff some things inside for added space.

As for finding a wheel if you decide you want one, most spares are just less expensive steel. Sizes are pretty standard and you can find them at etrailer.com. A tire and wheel combo is often the same price or even cheaper than just a wheel alone. But it might not be a tire brand that you would want. A spare wheel doesn't really need to match, does it? You can move them later at a more convenient time and place.

FWIW I should carry two spares since the last time I had trouble I needed two. But I just carry one spare and hope I'll be able to limp into somewhere if necessary. That's what I did the last time.

Where we travel civilization isn't that far away, and I just hate the thought of hauling along more "stuff".

I used to carry the spare that came with the 5er and an additional unmounted spare in the basement storage. Had trouble finding the correct tire at one time.