[AK-KingBoost]

Does your truck have the traditional/normal transfer case setup (2h, 4h, 4L) or the two speed transfer case (2h,4A, 4h, 4L). If its the latter you can run the 4wd at any speed even on dry pavement without harming the system.
If its the traditional or normal set up and your under 55mph like you said you will be fine to you it 4wd all day if you wanted based on the road conditions... Mpg might go down some but I would rather lose a gallon of gas here or there vs losing grip and losing a gallon of blood...
I recommend putting weight in the bed of your truck right between the wheel wells. I have 600lbs normally during winter time in the bed (200-400lbs is enough). I can run 2wd most of the time and if it gets to questionable click it into auto 4wd or 4wd...

 

[AK-KingBoost]

Great info guys thanks! No 4 auto so I'll be doing the selecting myself as i see fit. And it sounds like since we're pretty much going straight the whole time since it's kind of a highway i won't have to worry about binding up in the turns because the roads not quite slippery enough I should be fine.
One last question I just thought of. How about the summer months how often do you put it in 4H to give it a little workout? And what if you don't have anywhere to do that other than dry pavement or rain?

Summer time is fun time Bro. Don't worry about engaging the 4h to keep things frosty and free moving. Just roll in 2wd and within reason of the road conditions. If you venture off road go until you need 4wd (Be amazed how far you can make it) or when you need the extra traction like a wet boat ramp. If you have the elect locking rear you could always use that first before going to 4wd (This is for slow and slippery conditions not drive pavement where traction is not a issue).