My 07 is just turning 230k. I tow an enclosed trailer probably 2k average per year. The key to making the last of the 5.9s live is religious maintenance. Being retired army I'm pretty anal toward PMCS.

So ever since owning the truck this is what I've done

Switched to AMSOIL synthetic at 17k miles. I change the oil religiously IAW AMSOIL recommended intervals which is every 5k. I use WIX filters. AMSOIL recommends more frequent oil changes on the 07.5 5.9s due to the internal EGR. Took some getting use to the oil being dark all the time. I change the fuel filter twice a year, spring and fall. I use the Cummins fuel filters.

Added EDGE power adder and aftermarket aircleaner. On average I keep the EDGE set on the stock setting. I get better fuel mileage.

Another area of concern is the turbo. Being the EDGE has a turbo timer I set it at 1 minute to allow the turbo to cool. When I'm towing I allow for more time, usually 4-5 minutes especially if I pulling hills. The EGTs run about 320 at shutdown.

Service the tranny every 35k to 40k whether it needs it or not. I always service the tranny before I tow. Band adjustment is a must

Added the Bullydog steering crossmember to address possible death wobble

OE brakes changed out at 50k. I average brakes changes around

Changed out OE front end at 100k. Also replaced front U joints. Recently had to change out the front end at 235k. I run KYB shocks which have a lifetime warranty.

I service the transfer case and rear end every 40k. I exercice the 4WD twice a year. When I lived in the NW I used the 4WD more often. Now, being in AZ it's used less frequently.
130k replaced trans modulator. Tranny was short shifting at low RPM

Did a fuel sample and tested at Cummins at 200k. No sign or leaky injectors. I plan taking another sample this spring.

Overall this has been a great truck. My only complaint is the front seats break down constantly. Getting ready to replace the foam buns and cover for the third time.

My first CTD was a 2WD 2001. My only complaint with that truck was constantly dealing with the lift pump and injector pump.