Frank, use of the co detector or any detector that is contaminated with substances has an effect on the life of the detector. The more concentrated the pollutant the shorter the life. This is not to say that a none used detector does not have a life span because it does. You would want to try to find the freshest detector available if you are going to keep it for many years.
I stumbled across this post but many more would be expecting to see a new discussion for your question. Try starting a new topic for new comments or questions in the future. Thanks.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7