SMD resistor maximum voltage: is 200V really a limiting factor?
Generally speaking SMD resistors have lower voltage ratings than through hole .The older larger through hole resistors were used in valve circuits.Whats done these days is placing several SMD resistors in a series string to get the voltage rating.Because SMD parts are machine placed in production the extra component count is not seen as a penalty.Remember that the price of machine placing one part is a very small fraction of the cost of through hole hand placement .Some SMD resistors have laser cuts on them to get the right value .This can mean focused electric fields that reduce the voltage rating.Hence length is not going to always mean a high voltage rating.