I've read abt that, too but its kinda conflicting. Like this one states it's valid for one year. http://nepal.um.dk/en/travel-and-residence/information-for-danes/consular-service/driving-license/

In any case, Nepali traffic men don't really care when you're driving a private vehicle. My buddy flashed out his driver's license and they didn't really care.

During my last trip,I took one issued by AAA and I was never stopped.