If I don't accept a friend request on Yahoo! Messenger, how long is that request still active?

What I mean to say is, that a person I've knew in past sent me a request, but I don't want to be so unkind and ignore the request, but I don't want to accept it either. So I had the idea to let the request "open"... and now, I would know, if this request lasts so long as I accept or ignore it, or hat this request something like an " active countdown" (for example 72 hours)