Account expired?

Hi, I was given a 3 month account at some stage a while ago, and as I understood it, my account would expire 90 days or 400 sounds after I started using it.

I haven't had any need for the account until to day, and so I logged on in order to start looking for appropriate sounds and all seemed well until I clicked in the specific category I was interested in whereupon I was informed that my account had expired. Is this so? I was not aware that my account would expire if it remained dormant but unactivated for a lengthy period.