Expensive resistors are not going to cure hiss, unless an existing resistor is "broken", in which case any fully functional resistor of the same value and equal or better voltage and wattage rating will also cure the hiss. What I am saying is that cheap or run of the mill resistors that are fully functional at their rated value in ohms are not the cause of hiss.
But apparently putting your JLTI in the closet for a few years did cure the hiss.