My personal opinion is that a certain amount of hand tuning at the factories was done on revolvers. A spare cylinder therefore may work but not well- that's just my hunch.
The only documented thing I ever found on the spare cylinder idea was in a book about Quantrill. Frank James picked up a Colt 1851 from a dead Federal soldier. The gun was too beat up to use so he just took out the cylinder and saved it. The assumption was so he could do a cylinder change but that is just an assumption- he might have figured he could sell it to someone.
The only documented thing I ever found on the spare cylinder idea was in a book about Quantrill. Frank James picked up a Colt 1851 from a dead Federal soldier. The gun was too beat up to use so he just took out the cylinder and saved it. The assumption was so he could do a cylinder change but that is just an assumption- he might have figured he could sell it to someone.