You may spot a pattern, the more successful the console the longer Nintendo keeps it in production
The first successful (market leaders) consoles produced
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nes 1983 to 1995 = 12 YEARS lifespan
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snes 1990 to 1999 = 9 YEARS lifespan
The next two console are considered a flop.
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n64 1996 to 2003 = 7 YEARS lifespan
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gcube 2001 TO 2007 = 6 YEARS lifespan
So the wii was released in 2006
If it was a flop I would expect it to last between 6 to 7 years, if a success for it to last between 9 to 12 years.
As the Wii has been the biggest success in Nintendo and console history I would expect it to last something like 12 years