The trick is to get registered for the whole duration of your stay... I've done this and not had any trouble, even when traveling and staying at various locations (different cities).
Unfortunately I have not been as lucky as you. On my first trip to Russia I had a three month registration in Tomsk. Then when we went to Sochi for a 10 day vacation the "local" hotel ($15 a night) didn't know how to register foreigners. They wanted me to go somewhere in the center of the city and register at an OVIR which I knew would be impossible because my "sponsor" which was then my fiance's mother was not on vacation with us! So I didn't go. And despite having a registration good through 3 months, I was forced to pay a 100 ruble fine at the airport for not having a 10 day registration in Sochi!So be careful with this trick. Although it will definitely work when you are leaving Russia. But since I was boarding a plane to another town in Russia it was obvious I was not leaving Russia. Similarly lying that I was in Sochi for less than 72 hours would probably have failed and got me a bigger fine. I did make the argument that it was the hotel that refused to register. The officer said fine, you'll miss your flight, we'll go to court, bring the hotel agent in, and if what you say is true, you won't have to pay the fine. In other words I paid the fine
