There's a big difference between major projects and adding features too.
Maybe this is not the right time for Yahoo to do 3 year products simply because they suck at it (I spent more than 3 years at Yahoo, and I spent most of that time trying to shepherd projects through to the point my engineering team would actually get a go-ahead; we were a service function without direct control of a product, otherwise we should've just gone for it rather than wait...), and practising on 6 month projects could still bring a ton of useful improvements or smaller services. One thing to keep in mind with Yahoo is that it has a vast array of sites and services just sitting there - I bet there's a ton of poorly monetized services that could get drastic upgrades in well below 6 months if there's just sufficient fire behind someones asses...
Then they can start trying to add the standalone world-changing stuff again later, if they're successful.
Maybe this is not the right time for Yahoo to do 3 year products simply because they suck at it (I spent more than 3 years at Yahoo, and I spent most of that time trying to shepherd projects through to the point my engineering team would actually get a go-ahead; we were a service function without direct control of a product, otherwise we should've just gone for it rather than wait...), and practising on 6 month projects could still bring a ton of useful improvements or smaller services. One thing to keep in mind with Yahoo is that it has a vast array of sites and services just sitting there - I bet there's a ton of poorly monetized services that could get drastic upgrades in well below 6 months if there's just sufficient fire behind someones asses...
Then they can start trying to add the standalone world-changing stuff again later, if they're successful.