01-04 = LB7 are the ones with the most Inj issues, otherwise pretty reliable
04.5-05 = LLY are the ones that some have had overheating issues while towing but I don't personally know of any that do. Their Inj are much better with just an occassional bad one. Nice reliability IMO.
06-07 LBZ and IMO these or LMM are best. At elevated HP there have been piston problems maybe moreso than the older lb7 n lly.
07.5-current = LMM and these or LBZ are the best yet IMO. They rarely have Inj issues, have good turbos, etc. Just nice trucks. One caviot to these LMMs have the dpf but they can be removed relatively easy through some tuning n exhaust upgrades.
Overall, I think the engine n trans longevity is good with any of them. Other common issues for all of them are front wheel
Hubs/bearings don't last real long, tierods are weak, transfer case may eat itself (search pump rub and you'll see what I mean but ive recently read this might been addressed on lmm trucks). The water pumps usually make it 100k then might go out on ya.
Overall though, IMO, these are pretty reliable trucks with good maintenance and keeping a good eye on em.
Cya