Moving On

There are many others options for interaction and adventure based in and around Aronburg. If the party want more social or political engagement, or prefer to drive off bandits, clear out raiders, chase down miscreants and rescue kidnapped citizens, Aronburg is a good base for spinning those out.
At some point, it is time to get back on the way toward the Upper Valley and the purpose of their quest. That makes it an excellent time to introduce elements connected to that theme. As it stands, the party is headed upriver to explore the Upper Valley of Aron's Bowl for signs of dragons, and to take action if it proves out that the winged terror is a threat to the people of the vale and by extension, the whole upper coast of the world. It is known that the far side of the mountains ringing the valley tower over the coast, so a vengeful dragon is a serious threat to trade.
Along the way, they discovered that a cult of dragon worshippers had secured an artifact and were working to gather followers for a major assault. Defeating them, the characters took the artifact and continued on their way. While they have had encounters related to this since, those have been ancillary to the main story line. Now, the time has come to start bringing those elements back into the main focus for this adventure arc.
The next 50 miles of the journey are along the Flushing River basin leading from Aronburg to Deadfall. Ordinarily, this is a long day's journey, although making it in two allows a more leisurely pace, and a chance to stay one more night in the lush valley before climbing up into the less hospitable Upper Valley. This will help with advancing the story as well in this case. An encounter with a traveling salesman on the road outside of town will lead to a mention of the necklace the party has had in their possession since the kobold shrine early on in their journey, and the indication that there is a wizard's tower in the mountains to the east that is rumored to hold great stores of information about dragons and their ilk.
This tower can be reached by taking a little used track up into the hills to the east near the town of Casper, about 20 miles from Deadfall. A late start leaving Aronburg will bring the party into Casper in the mid to late afternoon. If they choose to ask anyone in the town about the wizard, they will meet with a reluctance to speak. Rolling well on a Streetwise or Persuasion check (DC16) will give them a good chance to draw information out. Basically, they will advise the party against visiting the "mad mage", and insist they wait until morning, at least.
That choice is theirs, and a check in the mid-20s will give them enough information to see the advice as sound. If they go at night, they will have trouble following the track, and get hounded by undead and ethereal spirits along the way once they reach the mountainside. I suppose wolves would be there too...
The trail is hard to follow (DC 18 by day, DC25 by night), but good Survival checks will keep them on it. If they move at half speed, they can roll with advantage, but the journey will take the entire day/night instead of six hours. This means increased opportunities for encounters on the road. The townsfolk say away from the area at night, and are reluctant to get too close to the mountain even during daylight, so that most encounters are with wolves and undead spirits.