Half that interval is good.
Stick with that.
IMO, the varying ammount of driving conditions is too great to say "Change it at xxxx".
That's why everyone recommends 3,000 miles. Even in the worst possible conditions, most modern oils should be able to last 3,000 miles.
When it comes to a 15, 30 or more thousand dollar piece of machinery, you have to be a complete idiot to want to save money by not changing your oil. It is cheap insurance.
Remember, though.. your oil is only as good as your filtration system. Any and all oil is rendered useless if it has solid particles in it. The first line of defense is your air filter. A tight intake(meaning no leaks) is a must. The second line of defense is your oil filter. If it gets passed your air filter, it will end up in your oil. Just remember to change your air filter at the recommended intervals. This, combined with an above average oil filter and in your case, synthetic oil, is about as good as you can get without getting too fancy.
Stay away from K&N air filters if you want longevity. They do not filter better than stock paper filters.
With the Mobil1, you should be good for ~6,000 miles. Do some research and see if you can find a larger than stock oil filter that will fit your engine. OrganizedChaos's advice is sound, only if you can prove that your oil is lasting all the way until the 2nd filter change. If you decide on the 6k interval, the larger capacity filter will help, since a clogged filter is useless and permits the flow of unfiltered oil when it bypasses.
If you drive "spirited", take many short trips(less than 25 mins), live in an extremely hot, cold, or dusty environment, spend 80% of your time driving in the city/stop and go, regularly climb any long, steep grades that require a downshift, or anything else that can be deemed "Severe Service", you might want to consider a ~4000 mile interval. Seriously, you just can't change your oil enough, and without oil analysis there is just no way to tell. It is better to be safe than sorry.
Look in your manual. See if it has a "Severe Service" oil change interval recommendation, and unless you spend 80% or more of your time cruising the highways, start there.