I had a bad accident which resulted in 2/3rds of my left ring finger getting amputated and the end joint on my middle finger getting fused. Needless to say, I was on a lot of painkillers. 40 mg oxycodone per day for about two weeks, which gradually tapered down to about 5 mg as needed, which amounted to about 5-10 mg a day for maybe 4 months.
Like you, I got kind of tired of the large doses after a while. They made me feel kind of sluggish and lazy. Even when I had tapered down I really kind of resisted taking a second 5 mg dose in one day unless I felt there was a compelling need. It seemed to be more bad side effects and less good value.
I eventually ended up mostly taking a single dose in the morning; for some reason my hand hurt worst in the morning and even if it didn't, not dosing in the morning usually meant my hand hurt worse than normal by mid-day and it was harder to recover (more meds, more time) once it got painful.
Like you, that single dose in the morning seemed to have a kind of calming focus. I'm also a huge coffee drinker, so I would imagine the combination was the key. But I never really wanted another dose during the day. I couldn't recapture the effect from the morning. I just got sluggish.
Unlike you I took them all, probably past where I had a hard-core need, but when they were gone -- zero sense of any withdrawal symptoms. Nothing. My sense is that addiction requires big doses that keep your level up nearly 24 hours a day for weeks. Tiny doses, like 5 mg, once a day probably just can't produce a true physical dependence because you go "dry" after about 8 hours.
I'd probably keep taking them if I had them, but only once a day, and that may be the difference. People who get addicted don't have that "it doesn't work so well in the afternoon" effect; for them it works every time and they really notice it when it stops. I just had no interest in more, it worked against me.