Kusatsu Onsen bus

Hey

I am planning on doing a day trip from Nagano to Kusatsu Onsen.

I've already looked at the bus timetable for getting from Kusatsu Onsen to Naganohara-Kusatsuguchi Station.
I am looking at taking the 19:50pm bus from Kusatsu Onsen to NK Station.
The bus is ought to arrive at the station at 20:15pm This will allow me to catch the 20:33 train as I begin my journey back to Nagano.

My one concern, as this will be the last bus of the day and the last train that I can catch on my way back to Nagano. Is whether there could potentially be any delays during the bus journey?
It will be late January, and obviously, I wouldn't wish to miss my train. Which is why I've also been considering getting the 18:30 bus.

Thank you in advance for your help!

You will go nagano ekihigashiguchi to kusatsu onsen by nagaden bus,cost 3500 yen,140min

JR bus kanto will go from kusatsu onsen bus Terminal bound for nerima kuyakushomae bus terminal,stop at naganohara kusatsugu chi & naganohara shiten mae,take 23 minutes

If the road is not closed (e.g., by heavy snow) there should not be problem catching the last bus/train. But if there is heavy snow, you should know about it when you go to the Onsen.

I once made a trip between Nagano city and Kusatsu Onsen, thinking it would be a short trip due to geographic proximity of the two. Wrong! There is a bus from Kusatsu Onsen to Karuizawa, from where you can catch a Shinkansen to Nagano, but the last of that bus leaves even earlier (15:50?). Once you hop on the Shinkansen, from either Takasaki or Karuizawa, it will be a short ride to Nagano.