Well, future Russians will own Crimea, so that's controlling one of the most important links to the Mediterranean, as well as dominating the Black Sea. Probably worth it, in the long run. 

 Yeah but they had the naval base in Crimea already even before this started. And given that they control the whole of Crimea now, further invasion is unnecessary, no? 

 Yeah, I think they're done. Unless they want to let the North Koreans show off, a bit, as a favor. 

 Too right.