My experience in my several certified IB rides including SS1k, BBG, 100CCC(insanity) are that more than one partner is a drag on making the time for all runs except the SS1K. 1000 hours in less than 24 hours is not a difficult ride particularly if you run the interstates. The 1500 BBG requires 62.5 mph for each hour to make it. Done on the interstates it is not to difficult, but done on a combo of secondary roads and interstates it is progressively more difficult if you don't have a range of about 300 miles between fueling. The 100CCC is difficult but with proper time management of riding 20 hours and sleeping 6hours each day, it can be done without exhaustion, mostly mental and visual(ask me how I know!!)
I like riding with my buddy whom I have done the above listed rides. He is a great dedicated and motivated rider(HD heritage classic) and is a greater rider, never complains about anything. Biggest problem with riding with him is his HD needs gas about every 150-170 miles, while my 05 FJR with the Tanji cell can do over 400 miles.
My next BBG will be solo in the Red Hot riders Baby Butt 1500. Got to make some real progress as I expect from experience that the route will include lots of secondary roads.
Lengthy response, but I hope helpful.