Hotels generally only register people for the duration of their stay in that hotel (not just pre-paid). On a practical basis, this is not an issue as long as you spend less than 30 days in Russia. For instance, I will arrive in Moscow on October 1 (where I have a residence), fly to Kazan on October 2 and register at the hotel there, then go back to Moscow on October 5 and stay till October 20. I've never been challenged, nor have any of my clients in similar circumstances been challenged.

Marc David Miller