We returned from Auli to Joshimath at 3 PM and covered the distance of 470 Kms in single stretch of 18 hours. I'll recommend you not to travel in night due to following reasons, which we realized later.
1. Roads are dangerous, foggy, and it is nearly impossible to find help if the car breaks down.
2. After Devprayag, Uttarakhand police restrict the entry of cars and bikes.
Research well and plan your trip accordingly.