Downshifts getting herder when engine warms up

[PieEater]

Hi Fokkers - bike has done just over 60,000 miles and downshifts are starting to get harder to engage. I've adjusted the clutch cable from the top adjuster so there is some but very little slack, I've also adjusted the lever span outwards so the cable is being pulled in a bit more. Is it time to replace the clutch or is there something else I should be looking at first?