We count all Postcrossing accounts, even if the members have not logged in for a long time. Usage of the site varies a lot, and it’s common for people to go away for a few years and return to active later (you can see examples here), when life allows or they have more time to dedicate to this hobby.
However, bringing it back to the topic here, Postcrossing does not give out addresses of members who have not logged into the site recently. 