The primetime runs of "The Big Payoff", which aired on NBC in the summers of 1952 and 1953, also ran for an hour (8 to 9 p.m., per Brooks and Marsh).
I wonder whose idea it was to expand TPIR. Were CBS and/or G-T taking stock of the soap opera expansions in '75 and looking into whether games could be expanded as well, or was the idea developed independently?
TPIR ran for an hour during a test week from September 1 through September 5, 1975 (between the exit of
Spin-Off and the debut of
Give-n-Take). That gave G-T some time to work out what few bugs there were in the system. I don't know how long before the idea of an hour-long show had been under consideration, but they did a good job in making the full hour worth watching - it might have been just as easy to say, "Okay, we'll have seven people play pricing games, and the top two will still be in the Showcase." I think someone said here that Monty Hall was reluctant to expand
LMaD to an hour because there was no logical way to make the full hour more interesting than the half-hour was - would you just split the show in two and pick out a Big Dealer from each group?
I don't think the
Wheel of Fortune expansion was bad - two three-round games; one head-to-head game for the two winners; day's champion plays a bonus round similar to the one we all know and love - but I'm sure it was more rushed (November 3 for the test run, December 1 for full time) - and the first half-hour of the hour-long
Wheel ran against the last half-hour of
TPIR.
As for whether hour-long soaps inspired hour-long game shows, I've never seen anything in print saying that. But you've got to think it's easier to have one production crew responsible for five hours of programming a week instead of two and a half. I doubt the fees CBS paid G-T to produce the show doubled (and I'm pretty sure the salaries for the show's staffers didn't double, either).