3' is the Maximum attachment limit, I perfer to go about 24" so I don't make the AHJ break out their tape. When you go up to 30" and beyond the it starts to look long, or in this case two far for the eye to measure. Sometime I'll make a story pole to keep a constant measurement around if doing exposed work.
It just looks simple and professional to have a constant flow of straping.
JMO.
article 358 is for EMT Light gage steel with aluminum coating
article 342 is for IMC a little heavier steel that threadable.
Article 344 is for RMC real Steel also threadabke and also can have various protective coatings.