You can cut it if you want or let it go it all depends upon your desires. I'm growing my plants in enclosures and can't really let them get too massive but if you have the space I say let it stretch and be big and beautiful-I envy you! However, if the bottom is scragly and unattractive you can cut the stem down to 6-8" high and it will prout new vines from the main stalk and make a bushier plant (it will look like two) plus cutting it down may cause the roots to send up basal shoots from the soil.
Cuttings are easy if you keep them humid, moist and in good light and it's easy to wind up with a surplus of plants because you can make whole new plants from just a small piece of stem with only 2 leaves!
I like to take 2 node cuttings,
make diagonal cuttings along the vine between every 2-3 leaves (so there's more rooting surface area)
On each 3 leaf section cut off the bottom leaf close to the stem and about 1/2 of the top leaf or two.
then slit the stem in several places on the bottom end where the 1st leaf was cut completely off,
soak the stem peices in superthrive stress hormone (not a necessity) and then dip in Rootone (with fungicide) and place in a small pot of long fiber sphagnum, vermiculite, milled sphagnum peat, etc (any commercially available seedling/cutting mix without fertilizers should work) and put in a terrarium or cheapie plastic JIFFY propagation greenhouse. til you see two or so new leaves hen you can put it in a nice large pot try not to disturb the roots when you put it in it's "permanent" container.
And soon you'll be trying to find homes for 20 N. khasania clones!
have fun!
