If I recall the criteria for jersey retirement are...
1. Coach K's discretion but after that...
2. National award ; player of the year award (defensive or overall) or first team all-american?
3. Graduate
I don't recall time at Duke being an issue other than "see criterion number 1"
Of course if Duke retires too many numbers Coach K will be asking a lot of great players whether incoming players can wear their jersey number...I don't think that will ever happen