Carl n Susan wrote:
Your rims came from Tredit. They are guaranteed for life. That rim is no longer made. If you call them they will replace it (and usually it's neighbor to preserve the same look) with an option to buy 2 more (for the other side) at a reasonable cost. Not an uncommon problem described in detail on the free to join Montana Owners Club web site (montanaowners.com)
First thing I would look up Tredit as mentioned above and see about getting a replacement pair.
Then I would put on the spare and take a chance on not getting a flat during the trip. As to your other question, the spare will last just as long as the rest of the wheels.