I have experienced the same problem as you do, i drive E90 2005. I just bought it last month and my service indicator stay idle on 7000km ... i've driven it for almost 3500km and the service indicator still stay on 7000km.
Then i got problem with my oil level sensor which asking for oil top up again and again (although i checked there is no oil leak anywhere and i did top up when the computer said so). I went to the dealer and they had my oil level sensor replaced. When i ask them about the idle service indicator, they said that it is because of my oil level sensor is malfunctioning then the service indicator did not counting down.
But after i replace it, i drove my car for more than 200km, yet it still stay on the 7000km!!
Anyone have the suggestion or an answer to our problem? Thanks