justinm - don't really believe manufactures set their design standards for working components (engine, trans, drive axle) for life in terms of years but rather in terms of hours before major repair can be expected. - I believe the term used is MTBF - (mean time between failure) Most manufactures design with a target of 10,000 - 12,000 operating hours (not key switch on hours) with normal maintenance before major overall can be expected. Certainly, units will go longer than that and some shorter depending on the operations, services, envirmoment, opertors and the 3 dirties (dirty air, dirty oil and the dirty sun of a gun that didn't change them). As I was taught years ago "oil is always cheaper than metal".

When we look at hours on hourmeters the recording can vary widely from truck brand based on what the hourmeter is set up to record - some folks measure key on time (get them out of the warranty period) faster, some folks measure operator in the seat time, some measure engine running time and so on