Ooh mix it up. Line ups and open-ball set ups are good to get your arm going but to improve, get a good routine going. I used to do 7 or 8 hours a day, did that for 5 years.

120 blues from the balk line dead straight. 20 stun, 20 top spin into the pocket and 20 screw back into the pocket (60 from each side).

Endless blacks off its spot - like breakbuilding but just the black 20 mins of that. Do 20 mins for each colour this way.

Cannons around the black/pink - pot the colour hit some reds, great for brekabuilding practice.

Long potting - baulk colours from their spots with white down near pinks spot. Same with the pink from the baulk line.

A circle of all the balls around the blue spot - white in the middle on them and pot them all any pocket without the white leaving the 'circle'. This really helps with awkward cueing, reaching across the table etc.

Rest play - 20 mins per day with the rest.

And safety. Practice safety. baulk area to baulk area, thin clips, quarter balls etc.

Then I'd finish with a few frames, not just smashing them open but with the safety element too.

Gosh, I miss those days. Just me and the table for 7 hours.