FWIW, I did 5 interviews in 8 days last year that went like this:
Day 1: Get up, take subway from Brooklyn to UES, interview Cornell; Skip cocktail hour at end of day (okay, I stayed for 1 cocktail), grab cab on York, hightail it to LaGuardia, hop on plane to O'Hare, arrive ~11p local time, get rental car, drive 2+hrs to Madison, WI, check-in at on-campus hotel ~1:30a.
Day 2: Interview at UW-Madison (one of my favorite programs BTW). Meet wife who just arrived from NYC at hotel, have dinner w/ old friends who are both faculty @ med school. Go to bed early.
Day 3: Get up at 0dark30, drive 5 hours to St. Louis in snow storm (wife mostly drove, I mostly slept) for 8am start of interview at WashU. This is a Friday so spend w/e w/ in-laws in St. Louis.
Day 5: Drive to Chicago in another snowstorm.
Day 6: Day 1 of 2 at U Chicago
Day 7: Day 2 of 2 at U Chicago
Day 8: Interview at UIC. So tired I can't remember a single thing about the place. Seriously, that day was a huge blur and I basically couldn't think of anything else except going home and going to bed.
I then flew to Seattle on Day 9 and interviewed at UW on day 10.
Moral of the story is that 2 or 3 interviews in a 2-4 day stretch, assuming reasonable distance b/w them is not unreasonable. 5 programs in 8 days (or 6 in 10 days in 3 different time zones) might be a bit insane. I had a much easier time of it w/ 3 interviews in 5 days earlier in the season, all of them in New England, total distance ~400 miles driving.
Boston, NYC, SF/Bay, Chicago, DC, LA are all places where multiple interviews can be relatively easily linked. Just remember that you will get burned out. Even if you don't have to travel, by the end of it all they will all be a blur and you'll wonder why the view from the call room at Columbia included the Golden Gate Bridge and Space Needle and how you managed to get to MGH from O'Hare on the BART.
BE (now PE)