Honestly, I cannot think of any generation where within the first year could justify both consoles.
I would say the following.
Primary console: First year or two
Secondary console: Third or fourth year after a price drop
Tertiary console: Fifth of sixth year after couple price drops
For example I got a PS4 in November, and am thinking of adding a Wii U in next year or so. After that will be content for a while, if the X1 really surprises me and makes games I have to get maybe buy that in 2018-2020 range.








