How long to get through process in Moscow?

[Ruark 4]

My wife is a naturalized US citizen, preparing to bring her parents, who live in Russia, to the US to live permanently. The concern is that they are somewhat elderly (both in their late 70s) and live in Ekaterinburg, which is 1800 miles from Moscow, where they will have to go for the interview and medical exam. It would be difficult and expensive for them to travel to Moscow for all this, then return to Ekaterinburg instead of going on to the US.

We are trying to confirm how long they need to stay in Moscow to complete the whole process, so they can travel to the US from there, instead of going back to Ekaterinburg. It is our understanding that the medical exam takes 2 days to get the result. After the interview, how long does it take to actually get the visa so they can leave? We hear many mixed opinions on this. Some say you get it the next day, others say it takes 3 or 4 days. Some say you have to go to DHL to arrange to have it delivered - but where would it be "delivered" to if they were staying there? Can they just go back and pick it up?

Right now we're thinking they should plan on staying in Moscow for 10 days, to be sure they have time for everything. We would really appreciate any specific information regarding this subject.

Thanks very much