Re: Question regarding purge valve on KM
It doesn't really matter how tight you have the purge cap on there as long as the ball is sealing properly and has enough room to lift so you can actually purge. With a KM, it should be fine finger tight assuming you are using a purge cap that typically comes on KMs.
As for purging itself, it's personal preference really. If you manage heat well then you may never have to purge. Some people like to do a quick purge if they haven't taken a hit in a while, IOW the smoke has been sitting idle in the vase for too long.