I Footvaxed the flock in 2007 and haven't needed to do so since. I did them around this time of year but found the oily adjuvant caused considerable irritation, particularly in the tegs, some of which rubbed the area raw against low branches so we had to catch and treat the wounds every few days to stop the flies laying in them. If I needed to do it again I'd wait until Autumn. Fortunately we haven't seen footrot or scald since.