P2459 Diesel Particulate Filter Regeneration Frequency

[gator63]

Looking for answers, over the weekend made a trip from Louisiana to Bowling Green, Kentucky, pulling a camper back from Kentucky and then from Louisiana to Orlando, Florida pulling a camper back over a 4 day period. Topped off the DEF before leaving on the first trip with standard DEF, while on the way for the 2nd trip, couldn't find any standard DEF, added the Platinum DEF. Only took about 1-1.5 gals of DEF to top off. While on the way back from the 2nd trip, about 8 hours into the 10 hour trip, the check engine light came on. Once home, had a friend with diagnostic tool check code and it was the P2459. Can someone give me an answer as to why it all of sudden came on after all these miles and time? What could possibly be the issue?

Thx, in advance