For what it's worth, my wife and I submitted our application in early May (so it doesn't apply totally to your situation), and went on a 3-month vacation the next day. We didn't notify CIC. Our citizenship test was in late October, and we're both at Decision Made now, so I guess it didn't slow things up too much. If challenged, we would have told them the truth -- the fact that I was on parental leave gave us a chance that we would never have again to visit my wife's family (where we used to live) for an extended period. I had a job to come back to, and of course our house.