I'm the original owner of my 335i (had it almost 6 years now). Since new I've had a <2mi commute to work. I know what you're gonna say, why don't I just ride a bike... I'm in outside sales so often times I leave the office and drive it out and about for longer distances but a lot of the time I don't. In all this time I've not noticed any strange behavior as a result of all these short trips to work on cold starts. The original battery lasted about 4 years until I started getting low battery warnings on the dashboard. As far as maintenance goes I've always done oil changes twice as often as BMW service requires.
I say don't worry about it.