I think you are confused as to what this registration means and how it is done. First of all, your visa will remain valid unless it is explicitly cancelled by the Russian government. Visa validity does not depend whether you follow registration rules in Russia or not.

Now about registration. In Russia, citizens and non-citizens are supposed to register at the place they reside or temporarily staying. When you stay at hotels, they register you automatically once you present your passport at check-in. If you stay in a private citizen's home, that citizen is responsible with registering you at his/her address. Either way, as a visitor you are not expected to stand in long queues in regional Federal Migration Service centres or post offices to register yourself. Besides, if you are staying for less than 3 days, you are not even required to be registered at all. I suppose, you will be staying at hotels only during this trip?

I have never dealt with visa centres, but I cannot understand how they can physically register you in Russia. What address would they provide?