I feel like 6 years is right for a healthy console, but that is also the max. For a console that doesn't do as well, I can't blame them for starting again in less than 6 years.
Generations are more about timing than horsepower though. Anything longer than 6 years is too long of a wait regardless of the horsepower situation.
curl-6 bet me that PS5 + X|S sales would reach 56m before year end 2023 and he was right.
My Bet With curl-6
My Threads:
Master Thread, Game of the Year/Decade
Switch Will Be #1 All Time
Zelda Will Outsell Mario (Achieved)
How Much Will MH Rise sell?
My Bet With Metallox