I've had one running for around 8 months only being reset for occasional software changes. Its just coming up to 24 days since it was last reset. Its hooked up to the internet with an ethernet card and the data is pulled off it by a seperate computer system across town once a minute so It wouldn't matter if it did reset.
You can take a look at it yourself : http://majestic81.plus.com/
Or the seperate computer system doing the graphing : http://pluggy.is-a-geek.com/majestic.html