Not sure how many 1,000+ miles I have ridden in a day - never counted. On long trips we usually hit 700-800 miles or more as long as we feel ok. Burning as much daylight as possible, usually.
The longest I ever documented (gas reciepts/witnesses, etc.) - by both Long Distance Riders & Ironbutt were 2 back to back days:
1,210 on the 1st day & 1,195 on the 2nd day - total of 2,405 miles in 47 hours. Jacksonville, FL to San Diego, CA. Started out in the rain but first day only. Great ride. Round trip that week was just over 5,300 miles & a lot of fun!
Link to my 50 CC RideLast year did 4 rides that were 500+ miles in less than 12 hours - longest of those was 665 miles and the total for that day was 947 miles (16 1/2 hours).
Longest 2 up day - about 600 miles and quite a few with my BSR that are 500+.