Depends on how much smoke you want them to hold. I'd suggest splitting the amount that you're smoking into 3-4 groups. For ex. - take 4 cheap coffee filters, and put 1/4 cup of peppercorns in each filter. Smoke one filter for 4 hours, one for 8, one for 12, one for 16, etc. After the alotted amount of time, remove that filter, mark it for how much time in the smoke, and bag it! Take a few corns for a taste, and if you hit the amount of smoke you want, remove the rest, store together, and note the time/temp for the next smoke!!
Of course, the wood you're smoking with will make a difference as well! My preference is a mix of hickory & cherry!