We are in constant contact with our hosts in an effort to ensure that they are active.   Some can on occasion, for family reasons, not accept WWOOFers for a period, but this is not common.  We are increasing our hosts all the time and send infromation on new hosts to members via our mailing list.   You can subscribe to our mailing list on our website; just follow the links to "mailing list".  Many of our hosts accept WWOOFers all year round.