Well, to be honest I haven't studied Russian completely independantly, but I would say for the most part i'm self taught. The Russian program at our university is really really bad, as it consists of only one crazy teacher. This in itself is not bad, but when the instrumental case is taught by saying "just add -ом to the noun", I would say that you pretty much have to teach yourself

I think it is impossible to learn russian (or any language) completely on your own. You need to have some exposure and interaction with somebody who is either a native speaker, or somebody who is pretty fluent in the language. Without this, you may get to a point where you can read and write russian, but probably not anywhere close to being able to speak.

My best advice is this (for typical university student) - even if you have no experience with the language, try taking a summer abroad and studying russian in Russia. There are a lot of programs which offer classes taught in english, so you don't even need to know what your doing. You'll pick up things very quickly just by hearing it all the time, and it will give you a pretty good foundation to teach yourself after that.

As for the time frame - that depends completely on you. I know some people who can look at a word or phrase and they instantly remember its meaning. I, on the other hand, have to write things out a bit before I really learn new things, so it takes me a bit longer. And then there are always people who, I think, aren't able to think outside of their native language, which means its impossible for them to learn a foreign language.

Just my 2 cents, hope it helps.

tdk