I thought that typecasting might have been Bill's reason for not doing any more GB movies. Typecasting can affect some actors and actresses. Some good examples.
Don Adams: playing as Maxwell Smart, Agent 86 is what did him in. He once tried to get into a dramatic role, but he couldn't since he was thought of as Max. The only other big hit he did was being the voice of Inspector Gadget. After that, that was it for Adams.
Henry Winkler: Eeeeeeeeeeeeh! Arthor Fonzerelli, or better known as the Fonz, was his best role. Fans could only picture him as the great one in the leather jacket. Thumbs up for Happy Days, thumbs down for his bombed movies. The only other role I remember him in was the coach in Water Boy.
The entire cast of Gilligan's Island: all 7 castaways suffered. Everyone could only picture them as Gilligan, Skipper, Mr. Howell, Mrs. Howell, Ginger, the Professor, and Mary Ann. Tina Louise has always blamed the show for ruining her entire career.
Jim Varney: Hey Verne! My old buddy Ernest P. Worrel was his best role. His physical comedy basicly made his entire life the weird odd job guy. Because of his roles in Ernest movies, he had to get a screen test in order to play as Jeb Clampet in the Beverly Hillbillies. Varney was always regarded as the funny man, not the straight man.
Perhaps the best example of all. You never see him anywhere but commercials for TV Land. . . Adam West, the 60's Batman. Heck, a lot of the people who portrayed super heroes were always typecasted! That was supposedly the reason for George Reeves' suicide.