There are some variables here. We're out west and average about 10K-12K a year. We don't have a lot of hot and cold weather changes or wet weather. I change mine either once a year or cheat a little and let it go to 16-18 months or 16K.
If you get yours out at reasonable intervals, you could probably push to the 16K mark, recommended mileage, even though it may take you 18 months to get there. I wouldn't go past 18 months even if the mileage is under the recommended.
I do my fuel filters EVERY oil change, and my air cleaner between 18 months and 24 months.
Many forget about their air dryer filters and hydraulic fluid filters. Freightliner has intervals for those too.