I was wondering that myself the other day, so I searched in BYC, and came up with the average of every 6 months, starting with when they are 6 months old. Others do it in March and again in September. I don't know why they choose those two months, but it seemed to be the common theme.I actually was thinking about this the other day and forgot to ask. The recent post about Gape Worms reminded me. Is there a recommended schedule for worming chickens? Like once a year, twice a year - anything like that?