The first thing I'd do is disconnect the cables at the brake end.
Then ask a helper to move the parking brake handle up and down while you watch the cable ends for movement. At least then you can determine if the cable has seized.
If you find one or both that is/are sticking, I would replace the cables. Yes, you will have to remove a lot of things like the console, rear seat etc., but it is not a terribly difficult job. I've yet to see a seized cable free itself up by trying to work lubricant into the sheath. It may work temporarily, but will likely seize up again.

Also I don't think you can correlate whether a cable will ultimately seize up simply based on whether you use the parking brake or not. I always use the parking brake and have had to change a number of cables over the years.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig