I know of hot shot owner who put almost 489K on one truck, 390K on another both used truck stop Def with no reported Def deposits..
It's kind of a crapshoot on the DEF system, some people have good luck, others don't, and so far I've seen nothing that correlates.
My GUESS is that hot shot guys, and anyone who drives/tows a lot, has fewer issues because the DEF injector is CONSTANTLY working, it's never sitting and allowing the DEF to dry up and plug it up (have you ever noticed if you spill it, DEF dries white and kinda sticky?). If your diesel sits a lot or makes primarily short trips and isn't getting up to the right temps, you may start having problems more often.
Again, that's my opinion based on what I know about diesels and the associated systems, and what I know from the few people I know who have had DEF issues. My neighbor has a Duramax, he's had the DEF system replaced once and the DEF heater replaced 2-3 times, but he never drives it - it just sits there. On the rare occasions he does drive it, he is just running 5 miles or so up town. His dad daily drives his Powerstroke, but again only drives up town most of the time, and has had the DEF system replaced 2-3 times. My FIL's last Powerstroke he drove over 100k on before he traded it in, and never once had a DEF issue - but then he typically was driving a minimum of 20 miles every day and pulled a 43' toyhauler with it.
I'm the first person I personally know who has a CTD with a DEF system, so we will see how things shake out - but I daily it back and forth to work about 30 miles each way, so I'm not terribly worried about it.