Drivetrain Is my clutch cable stretching?

I have a non-adjustable clutch cable and a firewall adjuster. For the past couple weeks, every time I drive the car and have to use the clutch a lot (like stop and go traffic), I find that it becomes difficult to put into gear because the clutch is not disengaging all the way, and I have to adjust the firewall adjuster out which fixes the issue until the next time it happens. It's hard to tell if the adjuster is just threading back in as I use the clutch and causing this, or if the cable itself is stretching, or if there is something else entirely causing the issue. I will say that the adjuster is almost fully out by now. Will a cable replacement likely fix this or is something else going on?

I also want to know if you guys have any opinions on using a lubricant inside the clutch cable sheath to extend its lifespan and make it easier to operate.

Pulled the old cable and it was shredding itself on the inside, a bunch of the material in the sheath was coming out of one end as almost a powder. Definitely time for a replacement.