A 10 year deal sounds about right. Although I like the yearly rotation that The Super Bowl does.
I've never watched the Grammys award show, in fact I haven't watched any of these awards shows. I have however watched clips or monologues the day after.
By swapping these shows around they get a chance to hopefully inject some new creativity. Maybe they can make them interesting. One thing is for certain, CBS clearly didn't do anything to convince me to watch it, maybe Disney can.