is 11 y/o original spare still a spare?

I may be wrong but think that tires on an RV sitting parked for months at a time don't get the "lubricants" in the rubber circulated plus the sun attacks the rubber starting sidewall cracks. The ten year old original spare, or one taken off the rig after 5 years as a spare, should be OK to get you to the tire store but keep your speed down and listen for any thumping sounds that may signal tire coming apart.