NADA is generally high. Certain types and/or makes don't stay on the market especially if priced correctly.
I have a friend with a beautiful, pristine 7 year old high-end fiver for sale and has it priced under nada and has not had any offer and only 4 inquiries in 10 weeks.
I think a lot is price and brand driven as well as geographic regions, too.
RVTrader seems to be the best place with the most exposure. Price it fair, describe it accurately, and also look at the competition and their prices.
Good luck.
2018 GMC Sierra 3500 DRW 4x4 Duramax/Allison
2014 Lifestyle LS36FW
St Augustine, FL