Most I did was 7333 in 1 week, which was the final week, and I did that in 5 or 6 days. Dx was far enough ahead anyway, so I'd just stopped for the rest of the last weekend because it was bxp.
I have irl stuff to do during the week so I was timing everything around ticks and being on when I shouldn't, etc, lol

Couldn't help missing ticks sometimes though, was annoying.
Chance of disease is 10%~ across all herb types. There is supposedly a small chance that lower level herbs yield larger harvests, but it never came clear to me. I was doing Dwarf/Lanta/Torstol in preparation for the bxp weekend/50m Herb and was still managing 90+ runs often.