One level tsp of ground cumin seemed the optimum dose, and it lasted 3 days. Half a lvl tsp seemed less effective. Since it's so cheap and safe, I didn't bother to find the precise minimal dose required. Stale cumin was less effective, but those were whole seeds that might have been 5 to 10 years old.
I bought a fairly large amount when it gave me temporary remission the first few times I tried it, and it's not so delicious that I used it up quickly...
Taking larger doses increased the duration of the PEM blocking slightly. Three heaping tsps of cumin lasted 6 days instead of 3. Again, I didn't think cumin was so delicious that I wanted to take 3 heaping tsps of it at a time.
It was T2 or iodine that lost its effectiveness when I took it daily. However T2 does what it does for me, it requires an occasional jolt rather than a constant boost. Cumin seemed okay daily, but there was no need to take it daily. I don't think I tried taking smaller doses daily, or tiny doses multiple times a day.
I think I even just forgot to see if I got PEM after taking it!
Yah, that's the tricky part of blockers: you have to pay attention to something not happening. I'd taken cumin numerous times after that first effect that stopped working. I'd probably been blocked from PEM for quite a few days over the years, but it was only when I was
expecting bad PEM and found myself PEM-free that I checked to figure out why, and whether it was repeatable. Science starts with observation, so you have to pay attention.