How important is 'Consecutive'?
Consecutive looks nice but I am not sure there is huge actual value in it being consecutive. For instance I actually see Bill Tilden getting a 7th year as year end number one in 1931 after a 6 year wait as being highly impressive.
If Federer was to get the year end number 1 this year (a difficult but not inconceivable task) then would his 6 year end number ones be actually less that Sampras' 6 consecutive year ends. Sure consecutive is cool but it is also cool to re-claim number 1. In Federer's case it would be after a 3 year break.