I have a 180 day visa and was informed i could spend 90 days here in one half of the year then 90 days in the second 6 months. To cut a long story short i overstayed the first 90 days and was worried this would be a problem. After a chat with immigration before leaving for a holiday i was informed that it was no problem to overstay the 90 days and at most would be charged a small fine, However i was informed that if i overstayed the 180 days this would be much more serious . As it happened i was not fined and nothing at all was said at the Airport on departure and arrival back into Moscow.My 180 days are not up yet but soon. Hopefully my employer will now apply for a work visa . :-)