Take a look...great article.

http://www.canadiandriver.com/testdrives/05g35x.htm

Thanks canuck for posting the article.

Does anyone know if there is any harm done if SNOW mode is active at highway speed or for an extended period of time (say on a 3 hour drive)?

wut do u mean?
AWD is always on. it's full time AWD if u have X
u mean snow mode?

Yes vvn.

The manual says not use snow mode on hard, dry pavement. It is apparently in 50/50 power distribution. It may turn itself off after 12 MPH, but this is not certain. Someone did a normal 1/4 mile in snow mode.

Here is a link to a prior discussion:

https://g35driver.com/forums/g35-sedan-v35-2003-06/45318-g35-vs-g35x.html

Like Andy says it is supposed to turn off of snow mode at speeds above 12 mph., but why do you want to do this? When you slow down to the slower speeds (below 12mph) you are putting a lot of strain and stress on your drive train when you are not going in a straight line with snow mode on driving on dry pavement.