While I agree with those who've pointed out that irregular soldiers in guerrilla units used multiple revolvers to achieve firepower, and even most armed people at the time outside war, who carried and used percussion revolvers, might carry more than one if they believed extra firepower was useful, I'm not certain we can really tell from historical records that spare cylinder reloads was solely hollywood.
If it happened I think it was likely very rare and might not have been thought notable for those keeping recods. Those records might have been lost -- if they ever did exist. Even the most thorough history books present a bare skeleton view of what happened.
How much of what you do each day is historically notable?
For me, not much (Ouch! My poor ego!!!)
However many gun owners who did write about their gun use, would they note particular details? Apparently no one here has come across records of anyone changing out cylinders in any historical records
Also consider guns were expensive. How many could afford or wish to invest in extra cylinders, which might require hand fitting?
I'm saying "absence of evidence is not evidence of absence."
Don't get me wrong.....I'm certainly not saying it was commonplace. I think we've covered that.
But .... it might still have happened ... we'll just never really know, without the evidence.