IMO, it depends...
The long exposure NR function is "dark frame subtraction" (which is why it takes so long). The advantage of this is that it maps/removes sensor specific issues like hot pixels, which basic color/luminance NR in LR will not do so well.
I would say that you should do some testing to determine if/when there is a benefit to you.
BTW, those are rather long exposures... there might be another way of going about it that will minimize heat buildup/noise.