They have been issuing them sporadically the last couple of months for about 10 days at a time but I haven't noticed one for about a month now. Sign up for their promotional emails. And usually someone on here will post if they get a notification. Sometimes you have to add a coupon to your rewards account before you can get the 4x rewards. (That's been the case with the sporadically released deals the past couple of months).
And PP is right, the holiday one should be starting sometime in the next month.