Unlike most other Jin Yong heroes, Kiu Fung first debuted when his martial arts had already reached maturity. By the time he first appears in DGSD, Kiu Fung is already one of wulin's top fighters.
DGSD was not a long story as far as the timeline of events was concerned. Unlike a number of other Jin Yong novels, which span twenty or thirty years, DGSD covered a period of about two years.
During the time between his first appearance in DGSD and his death, did Kiu Fung's martial arts improve any? He certainly didn't learn any new martial arts techniques during that time, but did he improve his existing ones (discounting the DGSD Ed. 3 revision of Hong Lung 28 Palms to Hong Lung 18 Palms, which he apparently never had the chance to benefit from in a fight)?