You don't have to write anything at all.
The only people automatically removed are those who have never logged into the board after signing up. I give them a few months to login and then get shot of them so that the member list is a true reflection of the number of people that read this board. Or at least
have logged into this board at least once.
Actually posting a message is not compulsory. But it is nice to hear from people now and again.
What also happens automatically is if you change your email details in your profile the board throws you out automatically. This is because your email is part of the registration process.
Anyone that we realise has done this gets activated as soon as we notice. If we miss it for some reason or if something goes wrong and you can't access the board then you just have to let us know.