Mockingbirds typically repeat a phrase three or four times. What you describe doesn't sound that far out of the ordinary. I have heard mockingbirds with more extensive repertoires than others. I don't know if they learn new songs as they get older. Or, perhaps with more competition they need to try harder to impress the ladies.
It could also be a regional thing.
Could you record it and post it?
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to record your bird sightings.