code: public long getExpirationTime() {
  		if(!isValid()) {
  			throw new IllegalStateException("this sip application session is not valid anymore");
  		}
  		if(expirationTimerTask == null) {
  			return 0;
  		}
  		long delay = expirationTimerTask.getDelay();
  		if(delay <= 0) {
  			return 0;
  		}
  		if(expired) {
  			return Long.MIN_VALUE;
  		}
  		return this.expirationTime;
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipApplicationSession#getExpirationTime()