About 700 miles down I95 on a BMW R1100R (damn that short gearing....) two-up with gear.
About 700 miles down to Atlanta over-night on a Ducati S4RS with no gear.
About 550 to Knox County, TN over-night, with gear. (After only 3 days of riding a motorcycle, on my brand new BMW F800ST).
In each case I could have ridden more, but certainly wouldn't have enjoyed it.
I feel that 1,000 miles is my upper limit. After that it would be torture for me.