Note the word extremes of 10 degrees or more in either direction. Temps in the 40’s may generally be ok for some acclimated highlands but not for all. You will have to experiment growing different highlands to determine which will work best for you because too many variables will exist for anyone to definitely state that any specific Nep would be ok with repeated temperature drops into the 40’s nightly for the winter months. I find a year round drop into the 60’s at night to be optimal.Highlanders appreciate lower temperatures and fluctuation. In other words, they need a night time temperature drop. Daytime highs in the 70's to nighttime lows in the 50's are perfect. Extremes of 10 degrees or more in either direction for limited times seems to be acceptable. My acclimated plants can easily withstand night temperatures into the 40's without damage.