How many years would be too soon for a console to be taken away from us and put be put to it's death and how many would mean a console overstayed it's welcome?

I think 6 years is the minimum, or at least close to 6 years. Under 5 is definitely unacceptable.

5 and beyond is fine. Anything less is dissapointing.

If the market is heading towards mid gen upgrades like it seems then each revision of that hardware should be fully supported for 6 years imo after that its up to devs and whether they wish to support it futher.

Six years minimun. Wouldn't mind having lifespans of those like 360 and Ps3, which still were getting games ten years after their release.

5 years minimum. Anything less, and it's taken as a symbol that someone really did screw up with the console.

3 - 4 years is a good length of time. Beyond that they start to really hold game development back. Besides most studios will continue to release multi plat games for several years more anyways due to the install base. 

7-8 years is what i feel is acceptable.

5 years maximum.

5 years, any lower and makes the generation feel way too short, any higher and it drags on and causes migrations to PC.