The longest stretch without any hotel/motel may very well be the stretch between Brawley and Blythe which is about 69 miles. Unfortunately for east bounders, this is a somewhat difficult stretch.When I did this section several years ago (west bound in September), it was a hilly, very windy section. Luckily for us, we had it as a massive tailwind.
Additionally, the traffic was fairly busy on the narrow road and has in places very limited sight lines due to the continuous ups and downs (about 15'-20' each) east of Glamis. Worse, the traffic was primarily semis or large RV hauling dune-buggies (Glamis is a national off-road area due to sand dunes) on the narrow road. I had to bail off the road twice.
If I were to attempt it east bound, I would leave about 30 minutes before daybreak and pray for a side-wind. It is mostly flat until a few miles before Glamis. You have a long climb out of Glamis (1 store, HIGH prices, check hours) then the rollers start and last until maybe Palo Verde where it becomes fairly flat again. NOTE: Back then, No services at all between Glamis and Blythe so carry water. I guess you could stop in Palo Verde and ask for water. However, Google is now implying Palo Verde has a convenience store possibly. Definitely call the day before you head out to verify.
Note that there used to be a WarmShowers host near Palo Verde we stayed at but it was one of the more "interesting" ones I have stayed at and it was maybe 1 or 2 miles off route on very sandy road (fell once Laugh-In Show style, stopped repeatedly). There may be Air BnB or similar in the area now for all I know but there was not then.
Finally, maybe check a few journals over on CrazyGuyonaBike.com to see status of more recent trips.
Tailwinds, John