I'll second the thoughts on the only time a "slower" truck is a pain is when you're trying to pass someone... which leaves everyone cranky because of the turtle race, particularly when there are only two lanes.
I've only ever had one truck (the Columbia at Arrow) that ran faster than 65. My Arrow truck was cut at 75mph. I'll be honest, it was nice to have, but if someone offered me more money, I'd have cut that sucker back to 65 in a heartbeat. I never used the 75mph except passing on some of the Oklahoma turnpikes. Typically you'd find me at 65mph cruising with the company trucks. Out in west TX, NM, AZ, speed is nice. But I thank my "slow" trucks for keeping my driving record clean of speeding tickets.