A consoles life should be between 10 - 12 years.

During a generation a console should exect to see upgrades every 3 - 4 years as new fabrication process mature.

A new generation console should arrive around years 8 - 10, or once new tech is cheap enough to make a giant leal forward.

All and all, a console should see 1st party support through three revisions. support should be dropped for the oldest model after that which would be closing in ona decade. 3rd parties an yearly franchise can carry on, from there.

I don't think a console should remain on the shelves more than 8 years. With backwards compatibility remaining infinite going forward, you can always go replace you worn out device wth whatever model you want between $200 - $600.

As latest gen console: 5 years minimum, 6-8 years ideal.
As entry-level console after the successor is launched: as long as it keeps on selling enough to justify production and support.

15 years minimum

5-6 years before a successor is released I'd say. Although in some cases it might be smart to abandon a console earlier.

Time frame is the wrong way to look at it for me, I love technology, I love hardware.
It's the technological leap that is the important factor.

If you can get a 6-8x increase in performance for about $400-$500, then it's time for a new generation.

Ironically... Thanks to the skipping of 20nm at TSMC... Hardware took a massive jump in price/performance thanks to 14nm and we could kickstart the next generation early. - Not to mention that the Xbox One and Playstation 4 released with old, mid-range hardware which is showing it's age quickly.

Thus... For me it doesn't matter if we get a new console every year or every 10 years, just the upgrades better be worth it.

around 5+ years would be nice

I would say around 6 years is good.People need to realize that game development and hardware costs are taking more time to make/go down.We not only need longer generations so that the system get games, but also because it is no longer possible to release full generational leaps in 4 years at a "low cost".

Well, the Wii U lifespan is not acceptable.I mean, I got my money value out of it, but its lifespan is nothing short of dissapointing.But its understandable, since it didnt sold well.

Understandable is different than acceptable.