I'm looking at a 2004 C4500 crewcab Duramax with 250,000 miles. What kinda life should u get out of a Duramax? I know it depends on how it was taken care of and how I take care of it. What about the Allison with 250,000 miles? I'm currently using a 2006 2500HD to pull my trailer. I like the idea of having a larger truck in front of the trailer. I been reading some of the other post here also, now I'm woundering if there is no real advantage to go to a C4500. or any large med size crew cab trucks.