The new ones aren't very worn, maybe a year old if that, but that makes me feel more comfortable with it.. I'm dropping the tire off this AM and they said if they can fix it great, if not they can have a replacement in by tomorrow, so the only driving will be around Chestermere if absolutely necessary, so it works out well.
I'd get another one to have a spare of the same size, but the newer tires are wide enough that the cover for the spare well doesn't close with the bigger tire in it!
Thanks guys, I appreciate all the help.