I would definitely have paper maps with you at all times. You can either get a decent atlas, such as the Rand McNally, or individual state maps. We usually have BOTH. Our GPS, including the one on our phone, is very handy when trying to find a specific address such as a hotel or restaurant. Electronic maps online are great for getting exact mileages, but they are terrible about their travel time estimates, so we only use them for mileage planning purposes.
To comment on Dave's comment about not knowing what's between Limon and Aurora for lodging ... um, not much. The hotels in Limon are around Exit #361 and Exit #359. Airport Blvd., at Exit #285, is the next one (going west) that has definite lodging. There used to be a couple of motels in between but I noticed this summer that the recession hit that area pretty hard and closed at least one, and I don't remember which one. The reason I suggested Limon instead of Aurora is because in Aurora, you're on the east side of a big city heading west, and you'll probably get stuck in the midst of Rush Hour, Denver Style. Having just done that less than a month ago, I wouldn't recommend it. To stay west of the I-25 interchange, means you'd be driving more than that 605 miles that Google Maps shows. Ugh! Limon is a little further east, and by the time you leave in the morning and get to Denver, the traffic should have died down. If not, Airport Blvd. has a Denny's to sit in, have some coffee and wait it out.
Here's the part of our summer trip report that discusses the I-70/I-15 route, and shows you some photos:
2018 History Tour, start at post 32 (day 31).