60k for shocks, brakes etc, sound normal from y 40 yr experience with GM rigs.
Granted most of mine have been 8 luggers, I get 150-200k miles over 10 years generally speaking with no major issues using in construction.
My son has an 05 4.8 with 130k no issues. My 2000 C2500 I use more like a half ton now, no issues other than 20 yr old sensors etc going haywire.....
Just remember, frontal area and aerodynamics of a trailer can effect performance towing etc more than weight. 25k lbs with 70 SQ ft of frontal area needs 135 HP to gon60 on a level. 15k lbs with 90 SQ ft of FA ALSO needs a whopping 135 HP.
Marty