a complete truck alignment front and rears it is the only way to be sure and it is cheap at around $200 for the whole truck,just make sure the you have it done by people that align trucks for living, NOT the truck dealer
At the very least i have mine done once per year. but at any and i mean any sign that there may be a problem they are checked and fixed if needed.
I am a firm believer in maintaining a rig not only in matience but also in washing them and keeping them clean. ain't nothing worse to me than a dirty rig or one with the paint oxidising from lack of care. I can understand being in bad weather but if your driving around with the same dirt on a year later then you need to wash your rig,lol.
I gotta agree with Gator about trucks and dirt. I am a mechanic, and our fleet is mostly local. Hauling mainly dry bulk, some hopper bottom grain, and tankers of De-icer in the winter. All of the drivers are company workers and dont get paid to wash the truck so they could care less. But all the crap that gets caked on over time, plus the mag chloride here in Colorado makes electical/lighting fixes into a nightmare. Can we say bad ground? Corrosion?
Anyway, back to alignments. I do trailer axle alignments in the shop if there is indication of a problem, but power units are sent out to a local company. We base our alignment frequency on tire wear, driver input, and service inspections of the unit. Our frequency for alignments is prolly quite a bit higher than most folks as our facility is a transload yard. We off load product from railcars to trucks for delivery. All that crossing the tracks (yard is gravel not paved) takes a healthy toll on equipment.
I keep an eye on tire wear and do it as needed. Too be honest its been awhile. I run centrematics and they have really made a difference in some uneven steer tire wear I used to have. Everyone said I wasn't aligning enough, things were out of alignment, etc. Since I put them on 3 years ago I haven't aligned a thing.