Yes.
18/6 is optimum.
Nothing on planet earth is "designed" to function for days/weeks/months without sleep.
Your plant will need a dark period for a proper metabolism and normal functioning.
A 65 watt light is pretty well useless, to be honest. Your plant will grow, but it will be a bit like growing an elephant by feeding it bread crumbs.
Try lowering your light to about 8-12 inches, there is no risk of burning your plant with a 65 watt light.
Regards, Organoman.